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THE ANALYSIS OF PAINTS 

AND 

PAINTING MATERIALS 



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^Succe^sors to theBookDepaHrtients or the 

McGraw Publishing Company Hill Publishing Company 

Publishers of Books for 

Electrical World The Engineering* and Mining* Journal 

Engineering Record Fower and The Engineer 

Electric Railway Journal American Machinist 

Metallurgical and Chemical Engineering 



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• THE ANALYSIS OF PAINTS 



AND 



PAINTING MATERIALS 



.•.\ 



BY 



HENRY A. GARDNER 



it 



DIRECTOR, SCIENTIFIC SECTION, EDUCATIONAL BUREAU, PAINT MANUFACTURERS' 

ASSOCIATION OF THE UNITED STATES 



AND 



JOHN A. SCHAEFFER 

INSTRUCTOR IN CHEMICAL PRACTICE, CARNEGIE TECHNICAL 
SCHOOLS, PITTSBURG, PA. 



J -» _ » » «i >> 

J „«■».»* -j * ■# * 



McGRAW-HILL BOOK COMPANY 

239 WEST 39TH STRFET, NEW YORK 
6 BOUVERIE STREET, LONDON, E. C. 

1911 



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Copyright, 1910 

BY THE 

McGraw-Hill Book Company 



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•••••••••• 

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Printed by 

The Maple Press 

York, Pa. 



»*•" 



To 
Dr. Edgar F. Smith 

Provost-elect, University of Pennsylvania, 
whose teachings have been a source of in- 
spiration in our work, this book is dedicated. 



222495 



PREFACE. 



The authors are presenting in this book a series of selected 
methods for the analysis of materials used in the manufacture 
of paints. 

Acknowledgment is made to Walker, Mcllhiney, and others 
for several methods of importance, which have been included and 
correlated with new and valuable methods worked out by the 
authors. 

It is assumed that the reader is well versed in the ordinary 
quantitative methods used in analytical chemistry, and no 
attempt, therefore, has been made to explain such methods in 
detail. 

It is the hope of the authors that this book will prove of 
value to all those engaged in the manufacture or use of painting 
materials. 

December , 19 10. 



Vll 



CONTENTS. 



PAGES 

Chapter I. 
The Analysis of Dry Pigments 1-39 

Chapter II. 
The Analysis of Mixed Pigments and Paints 40-47 

Chapter III. 
The Analysis of Paint Vehicles and Varnishes 48-77 

Appendix A. 
Analysis of Bituminous Paints 78-88 

Appendix B. 
Paint Specifications 88-96 



IX 



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THE ANALYSIS OF PAINTS 

AND 

PAINTING MATERIALS 



CHAPTER I. 
THE ANALYSIS OF DRY PIGMENTS. I 

ZINC OXIDE. 

Zinc Oxide. — Zinc oxide contains approximately 8o per cent, 
of metallic zinc, the balance being combined oxygen. This 
pigment is completely soluble in acetic acid. Some varieties, 
however, contain a small percentage of impurities, such as 
lead sulphate, zinc sulphate, sulphur dioxide, silica, iron, and 
traces of metallic zinc. This pigment may be analyzed either 
gravimetrically or volumetrically. 

Weigh i gram into a beaker, dissolve in acetic acid, filter 
off any insoluble residue and determine the percentage of zinc 
in the filtrate by one of the following methods: 

i. Gravimetric Method. — Heat the acetic acid filtrate to 
boiling. Completely precipitate the zinc with hydrogen sulphide, 
and boil for ten minutes, having the solution ftt the end of the 
operation smelling strongly of hydrogen sulphide. Filter, wash, 
and dissolve the precipitate in hydrochloric acid. Cool, add 
sodium carbonate solution drop by drop until the solution 
becomes turbid.? Heat to boiling, add 2 drops of phenolphthalein 
solution and continue the addition of sodium carbonate solution 
until just alkaline, when the zinc will be completely precipitated 
as carbonate. Filter in a Gooch crucible, while still hot wash, 
ignite and weigh as zinc oxide. 

2. Volumetric Method. — Treat the acetic acid filtrate with 
ammonium hydroxide until alkaline. Then add hydrochloric acid 
until faintly acid. Three c.c. of concentrated hydrochloric acid in 
excess are then added, the solution diluted to 250 c.c, and 



• • • « . - 

z «. •. •• «■•*>' - 



•* * __** ^*** _ ** ^ • • • 



2 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

titrated with standard potassium ferrocyanide as in the standard- 
ization of the solution. This method is not applicable in the 
presence of iron or manganese. 

Standardization of the Ferrocyanide Solution. — Ten grams 
of pure metallic zinc are carefully weighed off and dissolved in 
hydrochloric acid. The solution is made up to I liter and a 
volume equivalent to .Y gram is measured out. The remaining 
solution may be kept for restandardizing the ferrocyanide solu- 
tion which, on standing, appears to change from time to time. In 
place of using the standard zinc solution, . 2 gram of pure metallic 
zinc may be used for each standardization. 

The ferrocyanide solution is made by dissolving 22 grams 
of crystallized potassium ferrocyanide in a liter of water. One 
c.c. of this solution will be equal to about .005 gram of metallic 
zinc. 

The indicator is prepared by dissolving uranium acetate or 
uranium nitrate in water until a faint yellow color is produced. 
A 5 per cent, solution will usually give a good end reaction. A 
number of drops of this solution are placed on a spot plate, and 
the end point determined by introducing a few drops of the 
solution which is being titrated. 

The acid solution containing . 2 gram of zinc is made faintly 
alkaline with ammonium hydroxide, using litmus paper to deter- 
mine the end point. Reacidify faintly with hydrochloric acid 
and add 3 c.c. of concentrated hydrochloric acid in excess. 
Dilute to about 250 c.c. and heat to about 8o° C. 

The hot zinc solution is divided into two equal portions. 
One portion is titrated by slowly running in a few c.c. of ferro- 
cyanide solution at a time, with vigorous stirring, until a few drops 
of the solution give a brownish tinge to the uranium acetate 
indicator on the spot plate. The remainder of the zinc solution, 
with the exception of a few c.c, is now added to the titrated 
solution and the end point again determined. The titrated solu- 
tion is now poured back into the original beaker containing the 
few remaining c.c. of untitrated solution. The titration is 
finished by adding two drops of the ferrocyanide solution at a 
time, testing for the end point after each addition. As the end 
point develops slowly, it is well to examine each spot, after 
standing for a brief time. The first one developing a brown tinge 
is taken as the end point. 



THE ANALYSIS OF DRY PIGMENTS. 3 

A blue color will appear in the hot zinc solution upon the 
addition of the ferrocyanide solution. This color gradually 
becomes lighter, and when the end point is reached changes to a 
white. By repeated titrations, this end point can be easily 
noted and serves to shorten the time required for the outside 
testing with uranium acetate. It, however, should not be taken 
as final, as the uranium acetate gives a more definite end point. 
The blue color will not be present in an excess of ferrocyanide 
solution. 

It is necessary to make a correction for the amount of 
ferrocyanide solution required to develop a brown color in the 
uranium acetate indicator when zinc is absent. This correction 
is deducted from the total amount of ferrocyanide solution used 
and will usually run between . i and . 2 c.c. 

BASIC CARBONATE— WHITE LEAD. 

Basic carbonate white lead (2PbC0 3 Pb(OH) 2 ) contains ap- 
proximately 80 per cent, metallic lead and 20 per cent, car- 
bonic acid and combined water, with traces sometimes of silver, 
antimony, lead, and other metals. The analysis of white lead 
can best be carried out by Walker's* method. 

(a) Total Lead. 

" Weigh 1 gram of the sample, moisten with water, dissolve 
in acetic acid, filter, and wash, ignite, and weigh the insoluble 
impurities. To the filtrate from the insoluble matter add 25 c.c. 
of sulphuric acid (1:1), evaporate and heat until the acetic acid 
is driven off; cool, dilute to 200 c.c. with water, add 20 c.c. of 
ethyl alcohol, allow to stand for two hours, filter on a Gooch 
crucible, wash with 1 per cent, sulphuric acid, ignite, and weigh 
as lead sulphate. Calculate to total lead (PbS0 4 Xo . 68292 =Pb) , 
or calculate to basic carbonate of lead (white lead) by multiply- 
ing the weight of lead sulphate by 0.85258. 

" The filtrate from the lead sulphate may be used to test for 
other metals, though white lead is only ra ely adulterated with 
soluble substances; test, however, for zinc, which may be present 
as zinc oxide. 

* P. H. Walker, Bureau of Chemistry bulletin No. 109, revised, 
U. S. Dept. of Agriculture, pp. 21 and 22. 



4 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

" Instead of determining the total lead as sulphate it may be 
determined as lead chromate by precipitating the hot acetic acid 
solution with potassium dichromate, filtering on a Gooch crucible, 
igniting at a, low temperature, and weighing as lead chromate. 

(b) Complete Analysis. 

" When it is necessary to determine the exact composition of 
a pure white lead, heat i gram of the pigment in a porcelain boat 
in a current of dry, carbon-dioxide-free air, catching the water in 
sulphuric acid and calcium chloride and the carbon dioxide in 
soda lime or potassium hydroxide (1.27 specific gravity). By 
weighing the residue of lead monoxide in the boat all the factors 
for determining the total composition are obtained. Figure 
the carbon dioxide to lead carbonate (PbC0 3 ) , calculate the lead 
monoxide corresponding to the lead carbonate (PbC0 3 ) and sub- 
tract from the total lead monoxide, calculate the remaining lead 
monoxide to lead hydroxide (Pb(OH) 2 ), calculate the water cor- 
responding to lead hydroxide and subtract from the total water, 
the remainder being figured as moisture. 

" This method assumes the absence of acetic acid. Thomp- 
son* states that acetic acid varies from o . 05 per cent, in Dutch 
process white lead to o . 7 per cent, in some precipitated white 
leads. It is then more accurate to determine the carbon dioxide 
by evolution; this is especially the case when working with a lead 
extracted from an oil paste, as the lead soap and unextracted oil 
will cause a considerable error by the ignition method. In 
determining carbon dioxide by the evolution method, liberate 
the carbon dioxide with dilute nitric acid, have a reflux condenser 
next to the evolution flask and dry the carbon dioxide with cal- 
cium chloride before absorbing it in the potassium hydroxide 
bulbs. 

(c) Acetic Acid. 

"It is sometimes necessary to determine acetic acid. The 
Navy Department specifications demand that white lead shall 
not contain 'acetate in excess of fifteen one-hundred ths of 1 
per cent, of glacial acetic acid.' Thompson's method* is as 
follows : 

*J. Soc. Chem. Ind., 1905, 24: 487. 



THE ANALYSIS OF DRY PIGMENTS. 



«< t 



Eighteen grams of the dry white lead are placed in a 500 c.c. 
flask, this flask being arranged for connection with a steam supply 
and also with an ordinary Liebig condenser. To this white lead 
is added 40 c.c. of syrupy phosphoric acid, 18 grams of zinc dust, 
and about 50 c.c. of water. The flask containing the material is 
heated directly and distilled down to a small bulk. Then the 
steam is passed into the flask until it becomes about half-full 
of condensed water, when the steam is shut off and the original 
flask heated directly and distilled down to the same small bulk — 
this operation being conducted twice. The distillate is then 
transferred to a special flask and 1. c.c. of syrupy phosphoric acid 
added to ensure a slightly acid condition. The flask is then 
heated and distilled down to a small bulk — say 20 c.c. Steam 
is then passed through the flask until it contains about 200 c.c. 
of condensed water, when the steam is shut off and the flask 
heated directly. These operations of direct distillation and steam 
distillation are conducted until 10 c.c. of the distillate require but 
a drop of tenth-normal alkali to produce a change in the presence 
of phenolphthalein. Then the bulk of the distillate is titrated 
with tenth-normal Sodium hydroxide, and the acetic acid cal- 
culated. It will be found very convenient in this titration, which 
amounts in some cases to 600-700 c.c. to titrate the distillate 
when it reaches 200 c.c, and so continue titrating every 200 c.c. 
as it distils over.' 

" If the white lead contains appreciable amounts of chlorine 
it is well to add some silver phosphate to the second distillation 
flask and not c^rry the distillation from this flask too far at any 
time. 

" The method used by the chemists of the Navy Department 
is as follows: Weigh 25 grams of white lead in an Erlenmeyer 
flask, add 75 c.c. of 25 per cent, phosphoric acid, distil with 
steam to a 500 c.c. distillate, add to the distillate some milk 
of barium carbonate, bring to a boil, filter, keeping the solution 
at the boiling point (it is not necessary to wash), add an excess of 
sulphuric acid to the filtrate and determine the barium sulphate 
in the usual manner; subtract 53 milligrams from the weight of the 
barium sulphate and calculate the remainder as acetic acid 
(BaS0 4 X 0.515 =CH 3 COOH). The object of this rather in- 
direct method is to avoid any error that might arise from fatty 
acids being carried over by the steam distillation. For white 



6 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

lead that has not been ground in oil, Thompson's method is to 
be preferred." 

Volumetric Method. — The following volumetric method for the 
determination of lead has been found by the authors to give ex- 
cellent results when the precautions given are carefully observed. 

A -5 gram sample is dissolved in 10 c.c. of concentrated 
hydrochloric acid and boiled until solution is effected. Cool, 
dilute to 40 c.c, neutralize with ammonium hydroxide. Add 
acetic acid until distinctly acid. Dilute to 200 c.c. with hot water. 
Boil and titrate with ammonium molybdate as given in the 
standardization of ammonium molybdate. 

Standardization of Ammonium Molybdate. — Four and one- 
fourth grams of ammonium molybdate are dissolved to the liter, 
so that each c.c. is equivalent to 1 per cent, of lead when . 5 gram 
sample is taken. Standardize with . 2 gram pure lead foil. Dis- 
solve the lead in nitric acid, evaporate nearly to dryness, add 
30 c.c. of water, then 5 c.c. sulphuric acid specific gravity 1 .84, 
cool, and filter. Drop the filter containing the precipitated lead 
sulphate into a flask, add 10 c.c. hydrochloric acid, sp. gr. 1 . 19, 
boil to complete disintegration, add 15 c.c. of hydrochloric acid, 
25 c.c. of water, and ammonium hydroxide until alkaline. Make 
acid with acetic acid and dilute to 200 c.c. with hot water and 
boil. Titrate, using an outside indicator of one part of tannic 
acid in 300 parts of water. 

The following precautions must be observed in carrying 
out this method. Calcium forms a molybdate more or less 
insoluble, and when calcium is present, results are apt to be high. 
However, when less than 2 per cent, of calcium is present and 
a high percentage of lead, there appears to be no interference 
from the calcium. This method is only good for samples con- 
taining more than 10 per cent, of lead. Should a lower percent- 
age of lead be present, it must be precipitated as the sulphate 
then redissolved and titrated as in the method of standardization. 

Carbonic Acid. — The carbonic-acid content of white lead 
may be determined by using the Scheibler apparatus, as follows: 

One gram of the dry pigment is placed in the small tube 
(B) contained in the flask (F). Dilute hydrochloric acid is 
placed in the flask (F) on the outside of the small tube. Water 
is brought above the zero mark in the tube (M), by forcing water 
from the flask (E) by means of the bulb (A). On opening the 



THE ANALYSIS OF DRY PIGMENTS. 



-Sirheibler Apparatui 



8 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

stopcock (D) , water is allowed to reach a level on the zero mark 
in the two tubes (M) and (N) . The flask (F) is then inverted and 
the acid is allowed to act on the sample. The gas evolved passes 
into the rubber balloon (H) which causes the water in the tube 
(M) to lower and that in (N) to rise. The pinchcock (K) is 
opened and the water is allowed to flow out of the tube (N) at 
such a rate so that the liquid in the two tubes will be on the 
same level, as nearly as possible. When the gas ceases to come 
off, the pinchcock (K) is closed and the apparatus allowed 
to stand for several minutes, after which the flask (F) is shaken 
several times so as to complete the action. After action has 
ceased, which should take place in from a half to three-quarters 
of an hour, the water in the two tubes is brought to the same 
level and the amount of gas which has been evolved is noted. 
It is essential that temperature and barometric readings be made 
at the same time, so that corrections may be made for errors 
arising from these factors. The calculation is made directly 
by referring to the volume of carbon dioxide evolved at the 
given temperature and pressure in the tables which are given for 
this conversion, making correction also for the absorption of 
carbon dioxide in dilute hydrochroric acid, the tables taking 
directly into account the errors arising from temperature and 
pressure. In some cases where calcium carbonate is present in a 
pigment made from dolomitic limestones, it is necessary that the 
contents of the flask be boiled, although this need be done only 
in rare cases. 

The following Dietrich tables are so arranged that the con- 
versions can easily be made. 



THE ANALYSIS OF DRY PIGMENTS. 



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i hJ 


V 


ct 


l a. 


) ee 


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CJ 


U 


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IO 



ANALYSIS OF PAINTS AND PAINTING MATERIALS. 



CO 

H 

A 

o 

•»* 

© 

Q 



O 

(0 



< 



o 






I 

o 

CO 

Q 



bo 

CO 



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p -^ i 


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ts « 


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M VO 


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is w 


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a © 


M to 


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ts N 


£3 tt-t 


a ^ 


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ts n 


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a "■> 


M CO 


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ts « 


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^- v© 00 O r*5 ^- v© 00 O >-■ fO ^\Q tsOO 0> O m « «o 

o aoo 00 N O W ^ t fO «mOO>00 N. NO «o i" 

oo is ts ts is is is ts is ts n n nO ^O \© vo so vo 

88888 88888 88888 88888 



s m too 00 
0> 0> oo is vO 
ts n ts ts ts 



O M CO ""> Is 

to to ^- to « 

ts ts is is ts 



00 O M W Tfr 

M M O Ov 00 
N is, NVO O 



to SO ts00 C> 
Is SO *0 Tf ro 
vO vO vO vO vO 



O O O Q O 
OOOOO 



8 8 8 8 8 8 8 8 8 8 



8Q O O 
O O O 



^■vOOnmco to vO 00 O « co *0 00 Ov O m « co ^- 

^00 n ts<o m ^ f^ ro « m O 0> 00 Is tsO io ^ fO 

ts ts ts ts ts ts ts ts ts ts ts ts vO vO vO vO vO vO vO vO 

88888 88888 88888 88888 



Q\NTfvO00 O « fO »0 is « Q H co ^ to vO ts 00 Ov 

00 00 is vO »0 io t|- fO « m O O Ov 00 Is « V) >t to « 

Is ts ts Is ts s is is n N ts is vO vO vO vOvO'O'O'O 

OOOOO O00OO OOOOQ OOOOQ 

OOOOO OOOOO OOOOO OOOOO 



Ttr—ONwro to ts 0> O W rf to ts 00 ON m « co ^ *0 

00 ts vO vo *o ^ c^ N « h OONOOtsvO vOm^-coN 

ts ts ts ts ts is ts ts ts is nO O O O 

88888 88888 88888 88888 



ts.ts.VO W> Tf 
ts.ts.tsts.ts 

M M M M M 

OOOOQ 
OOOOO 



n •*$■ to ts 
^- ro n m 

ts ts ts. ts is 

M M M M M 

OOOOO 
OOOOO 



v> O N <0 VO 

a aoo ts vo 

O O O O VO 

M M M M M 

OOOOO 
OOOOO 



vO ts 00 0> 
m t|- ro « « 
vO vO vO vO vO 

M M M M M 

O Q Q O O 
OOOOO 



Tt ts On m ro 

NO >0 IO ^ 

ts ts ts ts is 

M M M M M 

OOOOQ 
OOOOO 



tO is Q\ M « 

CO CI M M O 
Is Is ts ts is 

M M M- M M 

OOOOO 
OOOOO 



tJ- vO ts -> O 

O* 00 is vO vO 

vO vO vO vO vO 

M M M M M 

OOOOQ 
OOOOO 



m N ro ^" ^O 
IO ^- fO W m 

vO v© vO vO vO 

M M M M M 

o o q o q 
ooooo 



M 



N to , ^- 



vo vo is 00 0^ 



vO 

8 



O 

ro 
vO 

M 

8 



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vO 

o 
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o 

o 



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o 
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o 


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to VO 


ts 00 


Ov 


o 


CJ 


N 


CI 


N N 


N N 


w c< 


N 


fO 



THE ANALYSIS OF DRY PIGMENTS. 



II 



*0 

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■M 

o 

u 



w 

PQ 

< 



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n « 


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On m co »0 N QnmC*^vo N 00 ON M « ^ i 1 VIVO N 

cocowmO &i O^OO N vO to^rocow »-■ O On 00 N 

oooooooooo n n n n n n n n n n r» n« O <0 

8QQOO QQQQO Q Q Q Q Q OOQQQ 

OOOO OOOOO OOOOO OOO 



00 

NO 
NO 

M 

8 



^ O 00 O N ^»0 n a O oi ro to O N OOOnOwW 

co « m m O On 00 N O NO tO^-roWM O '^ ^ 00 N 

0000000000 n n n n n n n n n N n O O O O 

8QOQO OQOOQ QOOQQ OOQQQ 

OOOO OOOOO OOOOO OOOOO 



CO 

NO 

NO 

M 

8 



On m co to n 

« « M O On 

00 00 00 00 n 



On m « ^- vO 

00 00 N NO to 

N N N N N 



8 8 8 8 8 8 8 8 8 8 



N On O M <Nj 

^" CO CO W H 

n n n n n 

M M M M M 

O O Q O Q 
OOOOO 



co ^" m O n 

O On oo n >6 

N O O O O 



00 
to 

NO 



8 8 8 8 8 8 



^\0 00 Q n ^ O n On m N^-ioN©r> 00 On O m « 

«mO0Cn 00 N O to iO ^ ro O h O On OO 00 N O 

00 GO 00 00 N N N N N N N N N N N vO NO NO NO NO 

8QQOO QQQQO QOQQO QQOQO 

OOOO OOOOO OOOOO OOOOO 



CO 
iO 

NO 

M 

8 



On m co to r*. 

M M O ON 00 

« 00 00 N N 



On m co Tf O 
n n n n n 



n o- O « co 
co « « M O 
n n n n n 



^ ioO n oo 
On 00 N NO »0 
nO nO nO O nO 



8QOOQ QQQQO 

OOOO OOOOO 



QQOQO 

OOOOO 



8 8 8 8 8 



On 

NO 
M 

8 



TfNQ00O« tO OO O 1 h fO ^ iO NOO O x Oh«co 

m O On On OO t— O to tJ- 'fr coNmOOn 00 M NO <fl 

00 » n n s n n n n n n n n n O o O O O O 

8 M QOOQ OQQOQ OQOOQ OQOOQ 

OOOO OOOOO OOOOO OOOOO 



3 

NO 

M 

8 



On m co to n QvitcotovO 00 On « N co ^ i^O N00 

O O On 00 t— NONO»OTfco NmmOOn 00 NO lO t 

00 00 N N N NNNNN N N N N O OOO'OO 

88888 8 8 S 8 8 88888 88888 



On 
co 
O 

H 

o 
o 



°o 



« co ■**■ 



lO O N 00 On 



O M « CO ^ - 

N N W N W 



to O N 00 On 
N N « N N 



O 

CO 



12 



ANALYSIS OF PAINTS AND PAINTING MATERIALS. 



a 

o 

CO 

H 
o 

•c 



o 

CO 

o 

o 

< 



d 

o 

otf 
U 



% I 

u 



3 
u 

CO 

O 



O 

o 

CO 

« 

J 

o 

CO 

Q 

.s 

■a 

CO 



SB 
\0 On 



^\fi 00 O N ro V)«0 00 ^ H«ro^"»0 O N 00 O^ O 

N« »o V) ^ CO « M O ON 9>00 NO vi ^co«mm 

0000000000 00 00 00 00 tx r^. N N N N N N N N N 

88888 88888 88888 88888 



O 

o 




0\ H co vo N 

vO vp >o i 1 fO 

00 00 00 00 00 



00 w co ^ 
« « m O O 

00 00 CO 00 N 



\0 N00 & O 

oo n o vo »o 



w « co ^* vo 

^- CO « m O 






88888 88888 88888 88888 8 



fl-9 
S * 

lO On 
N « 



*$• O 00 O « to ifl^O 00 O m « co ^" vo O N 00 On Q H 

O VO *$• ** CO WmOOnOO OO NO V) <t co « m O O On 

0000000000 oo oo oo s s n n n n n n n n n n O 

88888 88888 88888 88888 8 



• 

a 




a 


00 
NO 


*■ 


• 


i.n 


On 


n 


« 



On m co vo N 00 O « fO V) O N On O H w fo ^ ICO N 

iO to * «*) « M M O On 00 NO v> >C 't CO « ■-• O On 00 

0000000000 0Q 00 00 N N N N N N N N N N NO O 

88888 88888 88888 88888 8 



a £ 

vo On 
N « 



rtOOOOW to V) NOO O MfOTfioO N 00 Q* H « 

iO 't ro f) « m O On 00 00 n O vo *$• co W w O O O* 00 

00 00 00 00 CO 00 00 N N N N N N N N N N N N O O 

8 § 8 8 8 88888 88888 888888 






d fl 

§ fO 

vr> 0> 

N W 



On 


H 


ro 


VO 


f- 


*■ 


-* 


~5 


« 


H 


00 


00 


00 


00 


00 


M 


M 


H 


M 


H 


o 


o 


o 


o 


8 


o 


o 


o 


o 



O O « ro to 

O O On 00 N 

00 00 N N N 



O 00 On O w 
O vo ^ ^t CO 



« co i* vo O 
CI M O On 00 
N N N O O 



r*^ r^ ^^ n r^ r^ r^ r^ »-i r— i ■- • i — • •— • •— • • ■— ■ 

OOQOQ OQOQQ QQQ22 
OOOOO OOOOO OOOOO 



N 
N 

o 

M 

o 
o 



a 


• l-t 


a 


vo 

-<* 


% 


On 


N 


W 



« 



•* O 00 o 

**• CO « « 

00 00 00 00 O0 

M M M H 

o o o o 

o o o o 



o 
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00 

H 

o 
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vo N On O 

On 00 N N 



8 



O 
O 



o 
o 



M 

o 
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h co Tf vo O 

O lO rf fO « 

M M M M M 

Q Q O O 
OOOOO 



N CO On O m 
M O On On 00 
N N O O O 

M M M M M 

8 8 8 8 8 



N 

o 

H 

8 



o 

u 



O M W CO "<$• 



VO O N 00 On 



o 



M <M CO "<$• 
« N C* C< 



vo O «>» 00 On 
n « « « n 





CO 



THE ANALYSIS OF DRY PIGMENTS. 



13 



■2 

a 

o 



w 

PQ 

< 



£d 

N co 



s •** 
6 % 

N 

n o 

N co 




S-5 



a 




00 


• 








n 


CO 



3 NO 

O O 

N co 



a .s 

NO O 

n co 



6 •-« 

s 8 

N 

NO O 

n co 



? 



O O\00 N 
On ON 00 00 00 



00 On M « co 
NO tr> 10 ^- co 

00 00 00 00 00 



>00 SCO On 

W H O Ov 00 

00 00 00 N N 



O H N CO ^f 

00 N« >0 T 

n n n n n 



10 

CO 
N 

M 



88888 88888 88888 88888 8 



^ NO 00 ON H 

O O^OO NN 
On 00 00 00 00 



CO ^* NO N 00 
NO »0 ^- co « 

00 00 00 00 00 

M 



O H N CO ^* 

N m O On 00 

00 00 00 N N 



ifl« noo a 

NO V) * fO CO 

r*. r» t^ c» i>» n 



88888 88888 88888 88888 8 



On H CO ^t- NO 

On On 00 NO 

00 00 00 00 00 

M 

o 
o 



00 ON M N CO 

10 ^ * f*5 N 
00 00 00 00 00 

M M 



V)\0 NOO Cn 
M O On 00 N 

00 00 N N N 



88888 88888 88888 



O M N CO ^ 

NO V) ^ t*5 

t^. t^. l>» N. 1^* 

H H H • W H 

8 8 8 8 8 



to 

n 

N 

M 

8 



^t- NO 00 O M 

On 00 N N NO 

00 00 00 00 00 

M M M M M 

8 8 



8 8 8 



CO Tf NO N 00 

IO ^* CO « H 

00 00 00 00 00 

M M M M M 

O O Q Q O 
OOOOO 



O m N co *$• 

m O On 00 N 

00 00 N N N 

M M M M M 

8 Q O O 
OOOO 



to NO N 00 On 

NO »0 ^- co « 

n. n. r^. t>. r^. 

M M M M M 

8 8 8 8 8 



O 
N 
N 

M 

O 
O 



On m co to O 
00 00 N NO »0 
00 00 00 00 00 



00 On M CO ^ - 
^» CO CO W M 

00 00 00 00 00 



lO NO N 00 On 

O On 00 N NO 

00 N N N N 



88888 88888 88888 



M N CO **" 

no to ^ co « 

l>» N. t^. N. t-* 

M M M M M 

8 8 8 8 8 



v> 

H 

N 
M 

8 



Tj- NO 00 O H 
00 N NO NO lO 

00 00 00 00 00 



CO »0 NO N On 
*$• co N M O 

00 00 00 00 00 



8 



H t«5 * Ifl 
On 00 N NO 
00 N N N N 



tO NO N 00 ON 

lO ^ CO N M 

N N N N N 

H M 



88888 88888 88888 88888 



N 
M 

O 
O 



ONHCOtriN 00OHCO** >fl NOO 0> O HWco^-to NO 

N N O to ^" co co N m O O\00 NO O to^-coNM O 

0000000000 0000000000 NNNNN NNNNN N 

88888 88888 88888 88888 8 



N co ** 



to O N 00 On 



O M « CO ^ 



mo noo a O 

NNNNN CO 



14 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 




Fig. 2. — Carbon Dioxide Apparatus 



THE ANALYSIS OF DRY PIGMENTS. 15 

The authors and de Horvath have developed the following 
method as a simple and more efficacious means of determining 
the carbonic-acid content of paint pigments. 

The method can be used in such cases where the substances 
to be analyzed evolve gases other than carbon dioxide; that is, 
hydrogen sulphide, sulphur dioxide, or organic matter. The 
apparatus used is shown in the accompanying diagram. A 
weighed sample of the substance is introduced into the Erlen- 
meyer flask (A). Into flask (B) is placed a 10 per cent, solution 
of barium chloride, more than sufficient to hold the carbon 
dioxide evolved, and 20 c.c. of concentrated ammonium hy- 
droxide free from carbon dioxide. If sulphides are present, it is 
sometimes advisable to pass the liberated gas first through a few 
c.c. of strong potassium permanganate. The flask (B) is warmed 
until completely filled with ammonia fumes. Flask (D) is a 
safety bottle containing the same solution as flask (B). Only 
in rare cases will any trace of carbon dioxide be noticed in the 
safety flask. After flask (B) is completely filled with ammonia 
vapor, make all connections and allow the hydrochloric acid 
to drop slowly from the separatory funnel into the decomposition 
flask (A). When effervescence has ceased, heat the contents 
of the flask until filled with steam. The delivery tubes and 
sides of the precipitating flask are then washed with boiling 
water, the flask is filled to the neck, stoppered, and the precipi- 
tated barium carbonate allowed to settle. Wash thoroughly by 
decantation, each time stoppering the flask to prevent any error 
from the carbon dioxide present in the air, and determine 
either gravimetrically, by conversion into barium sulphate, 
or volumetrically, by dissolving in standard hydrochloric acid 
and titrating the excess of acid used with standard potassium 
hydroxide. Calculate the barium found to carbonate and the 
amount of carbon dioxide from the found carbonate. The 
entire operation may be hastened by conducting a brisk current 
of air free from carbon dioxide through the entire apparatus. 

A few typical analyses of white lead, for impurities, are 
given. 



i6 



ANALYSIS OF PAINTS AND PAINTING MATERIALS. 



CO 

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73 



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d 

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CO 


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a 


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a 


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d t^ 


to 


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M 


o 


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o o 


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d 


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6? 




























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ei to 


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Insoluble 
Antimony . 


• 

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d 

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C/3 


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r/i 


ver . . . 
dmium . 


• 

b 


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Manganese 
Calcium 


CD 

X 
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d 
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THE ANALYSIS OF DRY PIGMENTS. 1 7 

Metallic lead which comes to the corroder may contain very 
minute traces of metals, such as silver, copper, bismuth, cadmium, 
antimony, arsenic, iron, nickel, copper, zinc, and manganese. 
Should an analysis of metallic lead be necessary, it can be best 
carried out by the methods outlined by Fresenius' Quantitative 
Chemical Analysis, Vol. II, pp. 584 to 593. The method is 
here omitted owing to the large number of references which 
must be necessarily followed in making an examination for the 
above impurities. 

Basic Sulphate — T^hite Lead (Sublimed White Lead). — Basic 
sulphate white lead shows approximately 70 to 75 per cent, of 
lead sulphate, 20 per cent, lead oxide, and 5 per cent, zinc oxide. 
The Hughes* method for the analysis of this pigment has, by 
long experience, been found to give the best results. 

Total Sulphates. — Mix in a beaker 1/2 gram sample with 3 
grams sodium carbonate. Add 30 c.c. of water and boil gently 
for ten minutes. Allow to stand for four hours. Dilute with hot 
water, filter, and wash until filtrate is about 200 c.c. in vol- 
ume. Reject the residue. By this reaction all the lead sulphate 
is changed to carbonate and the filtrate contain sodium sulphate. 

Acidulate the nitrate with hydrochloric acid. Boil, and 
add a slight excess of barium chloride solution. When the 
precipitate has well settled, filter on an ashless filter, wash, 
ignite, and weigh as BaS0 4 . 

Lead (Method 1). — Dissolve 1 gram of sample in 100 c.c. 
of a solution made as follows: 

Eighty per cent, acetic acid, 125 c.c. 

Concentrated ammonia, 95 c.c. 

Water, 100 c.c. 

Add this solution hot and dilute with about 50 c.c. of water. 
Boil until dissolved. 

Dilute to 200 c.c. and titrate with standard ammonium 
molybdate solution, spotting out on a freshly prepared solution 
of tannic acid. The details of this method are given under the 
analysis of basic carbonate white lead. 

Ammonium molybdate is a slightly variable salt, but a 
solution containing 8 . 67 grams per liter usually gives a standard 
solution: 

* L. S. Hughes, chief chemist, Picher Lead Co. 
2 * 



l8 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

i c.c. equals .01 gram Pb. 
Standardize against pure PbO or pure PbS0 4 . 

Lead (Method 2). — Treat sample as above until dissolved. 
If solution is not quite clear, filter. Add to filtrate an excess 
of potassium bichromate solution. Boil and stand in a warm 
place until well settled. Filter on a Gooch crucible, ignite below 
a red heat and weigh as PbCr0 4 . 

Factor for lead equals . 64. 

Zinc. — Boil 1 gram of sample in a beaker with the following 

solution: 

Water, 30 c.c. 

Ammonium chloride, 4 gms. 

Concentrated hydrochloric acid, 6 c.c. 

If sample is not quite dissolved, the result is not affected, 
as the residue is lead sulphate or precipitated lead chloride. 

Dilute to 200 c.c. with hot water and titrate with a standard 
solution of potassium ferrocyanide, spotting out on a 5 per cent, 
solution of uranium nitrate. 

Forty-three grams per liter of potassium ferrocyanide usually 
gives a solution approximately — 1 c.c. equals .01 gram Zn. 
Standardize against freshly ignited ZnO or pure metallic zinc. 

Sulphur Dioxide. — Digest 2 grams with frequent stirring 
in 5 per cent, sulphuric acid for ten minutes in the cold. 

Add starch indicator and titrate with N/100 iodine solution. 

A more accurate method is to add an excess of the standard 

iodine solution to the sample before addition of the acid and then 

to titrate the excess of iodine with N/100 sodium thiosulphate 

solution. 

\ Calculations. — Calculations can be simplified by bearing 

in mind the following relations: 

Weight of BaS0 4 X 1 . 3 = weight PbS0 4 . 

Deduct from the total lead the lead represented by the lead 
sulphate and calculate the residual lead to PbO. 

Calculate the Zn found to ZnO. 

Report the sulphur dioxide found directly, as it does not exist 
as a sulphite, but is instead an apparently occluded gas. 

Zinc Lead and Leaded Zinc. 

Zinc lead is approximately 50 per cent, zinc oxide and 50 
per cent, lead sulphate. Leaded zinc varies considerably in its 



THE ANALYSIS OF DRY PIGMENTS. 1 9 

composition, though it contains on an average 25 per cent, lead 
sulphate and 75 per cent, zinc oxide. Both are apt to contain 
traces of zinc sulphate, sulphur dioxide, arsenic, and antimony. 
The analysis of such compounds is carried out in the following 
way: 

Moisture. — Dry 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Lead and Zinc. — Treat one gram of the sample in a beaker 
with 19 c.c. of water, 10 c.c. of concentrated hydrochloric acid, 
and 5 grams of ammonium chloride. Heat on the steam bath 
for a few minutes, dilute to about 300 c.c, boil, filter, wash, and 
weigh any insoluble residue. In a pure leaded zinc or zinc lead 
compound no residue should remain. Examine the residue, 
should any be present. The lead is completely precipitated in 
the filtrate with hydrogen sulphide in the cold. Allow to settle, 
filter, wash, dissolve in nitric acid, evaporate in the presence of 
sulphuric acid, and determine the lead either volumetrically 
or gravimetrically, as stated in the analysis of basic carbonate 
white lead. The filtrate from the lead sulphide precipitate is 
made alkaline with ammonium hydroxide, any precipitate form- 
ing, due to the presence of iron, being filtered off, redissolved in 
hydrochloric acid, oxidized with a little nitric acid, reprecipi- 
tated with ammonia, washed and weighed. The ammoniacal fil- 
trate is made slightly acid with acetic acid, heated to boiling, and 
the zinc is precipitated as zinc sulphide, filtered, washed, and de- 
termined either gravimetrically or volumetrically, as stated under 
the analysis of zinc oxide. The operation may be hastened by 
titrating the zinc directly after the removal of the lead, as stated 
in the volumetric determination of the zinc. The filtrate, after 
precipitating the zinc as sulphide, is examined for calcium and 
magnesium in the usual way. Should calcium or magnesium be 
present, it is, of course, understood that the zinc must first be 
removed as sulphide before titration in order to determine the 
calc'um and magnesium present. < 

Soluble Sulphate. — One gram of the sample is boiled with 
100 c.c. of a mixture containing one part alcohol and three parts 
of water. Filter and wash with a similar mixture of alcohol 
and water, and determine the sulphuric acid in the filtrate by 
precipitation with barium chloride as barium sulphate. The 
sulphate thus found is calculated to zinc sulphate. Any zinc 



1 



'- •> 



20 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

remaining after the calculation to zinc sulphate is calculated to 
zinc oxide and reported as such. 

Total Sulphate. — One gram of the sample is treated with 
10 c.c. of water, 10 c.c. of strong hydrochloric acid, and 5 grams 
of ammonium chloride, in a large beaker. Heat in a steam 
bath for a few minutes, dilute with hot water to about 300 c.c., 
boil, and filter off any insoluble residue. Heat the filtrate to 
boiling and determine the sulphate present, by precipitation 
with barium chloride as barium sulphate, in the usual way. 
Calculate the total sulphate present, deduct from it the soluble 
sulphate, and calculate the remainder to lead sulphate. Any 
lead remaining after the calculation to lead sulphate is calculated 
to lead monoxide. 

The authors find the iodine test for the determination of S0 2 
in zinc lead and leaded zinc, as shown under the analysis of 
sublimed white lead, of great value. 

LITHOPONE. 

Lithopone is a chemically precipitated pigment containing 
approximately 70 per cent, barium sulphate, 30 per cent, zinc 
sulphide, with occasionally occluded impurities, such as zinc 
oxide, barium chloride, and barium carbonate. 

The following method after repeated trials by the authors is 
considered best for the analysis of this pigment. 

Moisture. — Heat 2 grams of the sample for two hours at 
105 C. The loss will be moisture. This should be less than 
one-half of 1 per cent. 

Barium Sulphate. — Treat 1 gram of the sample with 10 c.c. 
of concentrated hydrochloric acid. Add 5 c.c. of bromine water. 
Evaporate the solution to one-half its volume on a water-bath. 
Next add 100 c.c. of water and a few drops of dilute sulphuric 
acid. Boil, filter, wash, and weigh the insoluble residue which 
should show only the presence of barium sulphate. Examine 
the insoluble residue for silica and aluminum. Examine the resi- 
due as before stated. 

Total Zinc. — Determine the total zinc in the filtrate, either 
gravimetrically or volume trically, as given under Zinc Oxide on 
page 1. 

Zinc Sulphide. — One gram of the sample is digested at room 



THE ANALYSIS OF DRY PIGMENTS. 21 

temperature with ioo c.c. of i per cent, acetic acid for one hour. 
Filter and wash the insoluble residue. Transfer this residue to a 
beaker, boil with dilute hydrochloric acid, and titrate the zinc 
directly, as given under Zinc Oxide. The soluble zinc may also 
be determined in the nitrate by one of the methods, as outlined. 
Zinc soluble in acetic acid is reported as oxide; zinc insoluble, 
as zinc sulphide. The filtrate from the acetic acid treatment, 
after precipitating the zinc as zinc sulphide and subsequent re- 
moval, should be examined for barium which might be present 
as carbonate, and calcium, present as sulphate or carbonate. 
The presence of barium carbonate is unusual. The average 
amount of zinc present as zinc oxide in pure lithopone will 
usually be below 2.5 per cent., though sometimes as high as 
5 per cent. 

Soluble Salts. — Digest a 2-gram sample with 50 c.c. hot 
water and test the filtrate for soluble impurities. 

BARYTES AND BLANC FINE. 

These pigments are the natural and chemically precipitated 
forms, respectively, of barium sulphate. They vary in their 
percentage at barium sulphate, according to their purity. The 
content of barium sulphate should not be less than 95 per cent. 
The method as used for the analysis of these pigments is as 
follows : 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Loss on Ignition. — Ignite 1 gram of the sample for one- 
half hour. The loss will be organic matter, free and combined 
water, and carbon dioxide from any carbonate present. This 
loss should be reported as loss on ignition. 

Barium Sulphate. — Treat i gram of the sample with 20 c.c. 
of dilute hydrochloric acid. Boil, evaporate to dryness, moisten 
with hydrochoric acid, and take up with water. Boil, filter, and 
wash. Should lead be present in the insoluble residue, as shown 
by the action of hydrogen sulphide, treat the insoluble residue 
with a little 1 : 1 hydrochloric acid and several drops of sulphuric 
acid. Filter, wash, and weigh the insoluble residue. Should 
lead be absent, the last treatment may be omitted. Treat the 
insoluble residue after washing with an excess of hydrofluoric 



22 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

acid and a few drops of sulphuric acid. Evaporate to dryness, 
ignite, and determine any loss. This loss will be silica. Ex- 
amine the filtrate for aluminum oxide, iron oxide, and calcium 
oxide in the usual way. 

Soluble Sulphate. — Soluble sulphates should be determined 
by treating i gram of the sample with 20 c.c. of dilute hydro- 
chloric acid. Dilute with 200 c.c. of hot water, boil, filter, wash, 
and determine the sulphate with barium chloride in the usual 
way. Calculate to calcium sulphate. If carbonates are present, 
as shown by effervescence with hydrochloric acid, calculate the 
remaining calcium oxide to carbonate. If absent, report as 
calcium oxide. 

WHITING AND PARIS WHITE. 

These pigments are the natural and artificial forms, respect- 
ively, of calcium carbonate. Dissolve one gram in hydrochloric 
acid, filter, determine the calcium in the filtrate, as stated, 
under Gypsum. Determine the carbonic acid by the author's 
short method, as outlined under the estimation of C0 2 . Deter- 
mine the impurities as usual. 

GYPSUM. 

This pigment comes to the paint trade in either the hydrated 
or burnt variety. The amount of water contained in this 
pigment should therefore be carefully determined. 

Total Water. — Ignite 1 gram of the sample to constant 
weight. The loss will be free and combined water, if carbonates 
are absent. 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. The loss will be uncombined water. 

Calcium. — Calcium is determined by one of the following 
methods : 

Gravimetric Method. — Treat one gram of the sample with 
dilute hydrochloric acid. Add 150 c.c. of water. Boil, filter, 
and determine the insoluble. Precipitate the aluminum ox- 
ide and iron oxide in the filtrate with ammonium hydroxide 
and determine in the usual way. The slightly ammoniacal 
solution is heated to boiling. A boiling solution of 25 c.c. satu- 
rated ammonium oxalate is added and the solution allowed to 



THE ANALYSIS OF DRY PIGMENTS. 2$ 

stand from one to two hours or boiled continuously for one-half 
hour. Filter off the precipitated calcium oxalate, wash with 
boiling water, and ignite for fifteen or twenty minutes with a 
Bunsen burner to constant weight. Weigh as calcium oxide 
and calculate to calcium sulphate. Determine the magnesium 
in the filtrate in the usual way. 

Volumetric Method. — The method as outlined by Treadwell 
and Hall* is excellent. "The calcium is precipitated in the form 
of its oxalate, filtered and washed with hot water. The still moist 
precipitate is transferred to a beaker by means of a stream of 
water from the wash-bottle, and the part remaining on the filter 
is removed by allowing warm dilute sulphuric acid to pass 
through it several times. To the turbid solution in the beaker, 
20 c.c. of sulphuric acid 1 : 1 are added and after dilution with hot 
water to a volume of from 300 to 400 c.c, the oxalic acid is 
titrated with N/ 10 potassium permanganate solution. One c.c. 
of N/10 KMri0 4 =0.0020 gm. Ca." 

The sulphuric-acid content is determined by dissolving 1 gram 
of the sample in concentrated hydrochloric acid, precipitating 
and weighing as barium sulphate, in the usual way. . 

Silica Pigments: Silex, Asbestine and China Clay. — The use 
of the microscope in making a rough examination of these 
pigments is very valuable, as they all show different characteris- 
tics, the asbestine being long and rod-like in its particle shape, 
the china clay tabloid in shape, and the silica in small, sharp 
particles. 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Loss on Ignition. —Ignite 2 grams of the sample in a plati- 
num crucible for one hour. The loss will be water, unless a 
large amount of carbonate is present. 

Complete Analysis. — One-half a gram of the sample is thor- 
oughly mixed with 10 grams of sodium carbonate, and 1/2 gram 
of potassium nitrate, in a platinum crucible, and fused until clear. 
Cool, dissolve in water in a casserole. Make acid with hydro- 
chloric acid, having the casserole covered with a watch glass. 
Carefully clean out the crucible with a little acid, adding this acid 
to the main solution. After effervescence has ceased, evaporate to 
dryness on the sand bath. Cool, moisten the residue with a few 
♦Treadwell and Hall, analytical chemistry, Vol. II, page 491. 



24 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

drops of hydrochloric acid, and repeat the evaporation to dryness. 
Add a few c.c. of concentrated hydrochloric acid, allow to stand 
for a few minutes, and add about 10 c.c. of hot water. Filter, 
ignite, and weight as silica. This residue, after weighing, should 
be treated with an excess of hydrofluoric acid and a few drops 
of sulphuric acid. Evaporate to dryness and ignite. The loss 
will be silica. Any residue which remains in the crucible should 
be again fused with sodium carbonate and the fusion added to 
the original filtrate. If barytes is found to be present, the origi- 
nal sodium carbonate fusion is dissolved in hot water and the 
barium carbonate filtered off, dissolved in hydrochloric acid, and 
precipitated as barium sulphate in the usual way. This filtrate 
is then added to the original solution and the silica then dehy- 
drated. The iron oxide and aluminum oxide are precipitated 
in the filtrate with ammonium hydroxide, washed and weighed 
in the usual way. The precipitate of iron and aluminum oxides 
is fused in a platinum crucible with potassium acid sulphate solu- 
tion, the fusion taken up with water, treated with concentrated 
sulphuric acid, and the iron titrated, after being reduced with zinc, 
by means of potassium permanganate. The difference between 
this iron oxide and the combined weight of iron and aluminum 
oxide is the alumina. The filtrate from the iron and aluminum- 
precipitation is treated with ammonium oxalate, and the calcium 
determined as described .under gypsum. The filtrate from the 
calcium is tested for magnesium with sodium hydrogen phos- 
phate, and determined in the usual way. Carbon dioxide pres- 
ent is determined in a separate sample, as before given. The 
amount found is calculated to calcium carbonate. Any excess 
of calcium is reported as oxide. The magnesium is calculated as 
magnesium oxide, unless the carbon dioxide is in excess of the cal- 
cium present, in which case it is calculated to magnesium car- 
bonate, and the remainder of the magnesium to the oxide. 

Sodium and Potassium. — Mix i gram of the sample with 
one part of ammonium chloride and eight parts of pure calcium 
carbonate. Heat to dull redness and thus convert the sodium and 
potassium to chlorides. Cool, take up with water. Filter and 
precipitate the calcium with ammonia and ammonium oxalate, 
and again filter and wash. Evaporate to dryness in a weighed 
platinum dish, on the water bath. Take care to avoid spattering, 
as dryness is reached. Finally heat with a Bunsen burner to a 



THE ANALYSIS OF DRY PIGMENTS. 25 

very faint, red heat. Cool and weigh. This weight represents 
the total potassium and sodium as chlorides. Take up the resi- 
due in water and add an excess of platinic chloride solution. 
Evaporate to small volume, take up with 80 percent, alcohol, filter 
in a Gooch crucible, wash with alcohol. Dry in the steam oven. 
Calculate the potassium in the potassium platinic chloride to 
potassium oxide and then to potassium chloride. The difference 
between the potassium chloride and the combined weight of the 
chlorides is the sodium chloride which may then be calculated 
to sodium oxide. It is well to convert the chlorides of sodium and 
potassium into sulphate, after the original chloride solution has 
reached a small volume, by the addition of a few c.c. of sulphuric 
acid. The sulphates of these metals are less volatile than the 
chlorides, and greater accuracy can be obtained by this method. 
After weighing, the potassium is determined as before stated. 

OCHERS, UMBERS, AND SIENNAS. 

Mannhardt's* method for the determination of these pigments 
is an excellent one, and follows: 

" One gram of pigment is treated with 20 c.c. of 1 to 1 hydro- 
chloric acid on the steam plate in a covered beaker. Small 
amounts of stannous chloride crystals are gradually introduced 
into the hot liquid until the solution and insoluble are nearly 
colorless and the iron is all reduced to the ferrous state. (In 
umbers, which all contain manganese, this should be removed 
as Mn0 2 .2H 2 by boiling with excess of ammonium hypo- 
bromite in ammoniacal solution before taking up the reduction 
with stannous chloride.) The ferrous and stannous chloride 
solution is now stirred into 10 c.c. of 6 per cent, solution of 
mercuric chloride to remove the stannous salt. An equal bulk , 
of strong hydrochloric acid is then added and the solution titrated 
with 3 N/10 bichromate using a pale yellow solution of ferri- 
cyanide as external indicator. Nearing the end point, more 
acid is added, to bring the solution to an olive color. One c.c. 
3 N/10 equals .024 grams Fe 2 3 . Raw siennas may contain some 
ferrous iron. This is determined by dissolving 1 gram of pig- 
ment and 1 gram of bicarbonate of soda with hydrochloric acid, 

* Hans Mannhardt, Select Methods of Paint Analysis, pp. 22 and 23. 



26 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

using a small flask provided with a Bunsen valve. The ferrous 
iron is then titrated directly. One c.c. 3 N/10 equals .0216 FeO. 

"The hydra ted peroxide of manganese is best determined 
as manganous pyrophosphate Fresenius Quant., Vol. I, page 297. 

" The complete analysis of an ocher, umber, or sienna requires 
the fusion method of solution. In the interpretation of results 
any alumina is calculated to clay and the excess silica returned as 
such. The loss on ignition is determined on a separate sample 
and is made up of moisture (organic matter sometimes), the 
combined water of the clay, and the combined water of the 
limonite 2Fe 2 O s . 3H 2 0. The Mn s 4 of the raw umber is probably 
also hydrated. Burnt ochers, umbers, and siennas of course 
carry very little free and combined water.' ' 

IRON OXIDES. 

(Venetian Red, Metallic Brown, Indian Red.) 

Test for free sulphuric acid, by boiling in water, filtering off 
and using litmus paper. Estimate the amount by titration. 

Walker's* method for the analysis of oxide and earth pig- 
ments, which also includes the analysis of ochers, umbers, and 
siennas, is as follows : 

" Iron oxide is extensively used as a paint. The native oxide 
naturally varies very much in its composition. In general, 
however, only the poorer grades of native hematite are used as 
paints. Artificial iron oxide pigments, made by calcining 
copperas, may be practically pure ferric oxide. Umbers, ochers, 
and siennas are earthy substances containing iron and man- 
ganese oxides and more or less organic matter. 

"The methods of analysis are very much the same as those 
for iron ores. It is generally sufficient to determine moisture, 
loss on ignition, insoluble in hydrochloric acid, ferric oxide, and 
manganese dioxide. If much organic matter is present, roast 
2.5 grams in a porcelain dish at a low temperature until all 
organic matter is destroyed, add 25 c.c. of hydrochloric acid, 
cover with a watch glass, and heat on the steam bath for two 
hours; then add 10 c.c. of sulphuric acid (1:1), evaporate, and 

* P. H. Walker. Bulletin No. 109, revised, Bureau of Chemistry, 
U. S. Dept. of Agriculture, pp. 33 and 34. 



THE ANALYSIS OF DRY PIGMENTS. 27 

heat until fumes of sulphur trioxide are evolved and all the 
hydrochloric acid is driven off. Cool, add 50 c.c. of water, boil 
until all of the iron sulphate is dissolved, filter into a 250 c.c. 
graduated flask, fill to the mark, mix, and take out a portion of 
50 c.c. for iron determinations. For the determination of iron 
reduce with zinc, titrate with standard potassium permanganate, 
and calculate to ferric oxide. For the determination of manga- 
nese transfer 100 c.c. of the solution (corresponding to 1 gram) 
to a 500 c.c. flask, add sodium hydroxide solution until nearly 
but not quite neutral. Then add an emulsion of zinc oxide in 
water in slight excess, shake until all of the iron is thrown down, 
fill to the mark, mix, let settle, filter through a dry paper, and use 
portions of 100 c.c. (corresponding to 0.2 gram) for the manga- 
nese determination. Transfer to a 300 c.c. Erlenmeyer flask, 
heat to boiling, titrate with standard permanganate. The flask 
must be shaken during the titration and some experience is 
necessary to determine the end point, which is best seen by 
looking through the upper layer of liquid and observing when the 
pink tinge from the permanganate does not disappear on shak- 
ing. A standard potassium permanganate solution, the iron 
factor of which is known, may be used to determine manganese. 
The iron factor multiplied by o. 2952 gives the manganese factor. 
In some cases this method of attack will not separate all of the 
iron from the insoluble matter. In such a case the insoluble 
must be fused with a mixture of sodium and potassium carbon- 
ates, dissolved in water, evaporated with excess of sulphuric 
acid, filtered from the insoluble, and this solution added to the 
first one. 

" Another method is as follows : Roast 5 grams of the powder, 
digest with 25 c.c. of hydrochloric acid, evaporate to dryness, 
moisten with hydrochloric acid, dissolve in water, filter, and 
wash the residue; ignite the residue in a platinum crucible, add 
sulphuric acid and hydrofluoric acid, drive off the latter, and 
heat until copious fumes of sulphuric anhydride come off. Add 
potassium hydrogen sulphate and fuse, dissolve in water, filter 
from any remaining insoluble (barium sulphate), unite the two 
solutions, make up to 500 c.c. and use aliquots for the iron and 
manganese determinations. For the determination of iron place 
100 c.c. in a flask, add about 3 grams of zinc, put a funnel into 
the neck of the flask, heat when the action slackens; if basic 



28 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

salts separate out add a few drops of hydrochloric acid. When 
all of the iron is reduced, add 30 c.c. of sulphuric acid (1:2), and 
as soon as all of the zinc is dissolved and the solution is cool, 
titrate with potassium permanganate. 

"For the determination of manganese use 50 c.c, evaporate 
to a very small bulk, add strong nitric acid and evaporate the 
hydrochloric acid; add 75 c.c. of strong nitric acid, which should 
be free from nitrous acid, and 5 grams of potassium chlorate, 
heat to boiling and boil fifteen minutes; then add 50 c.c. of 
nitric acid and more potassium chlorate. Boil until yellow 
fumes cease to come off, cool in ice water, filter on asbestos, and 
wash with colorless, strong nitric acid; suck dry and wash out 
remaining nitric acid with water, transfer the precipitate and 
the asbestos to a beaker, add a measured excess of standard 
solution of ferrous sulphate in dilute sulphuric acid, stir until all 
of the manganese dioxide is dissolved, and titrate the remaining 
ferrous sulphate with potassium permanganate. A ferrous 
solution of about the proper strength is made by dissolving 10 
grams of crystallized ferrous sulphate in 900 c.c. of water and 
100 c.c. of sulphuric acid (specific gravity 1 . 84) . This solution is 
titrated with standard potassium permanganate. The reaction 
taking place when the manganese dioxide acts on the ferrous 
sulphate is Mn0 2 +2FeS0 4 + 2H 2 S0 4 =MnS0 4 +Fe 2 (S0 4 ) 3 +H 2 0. 
Hence the iron value of permanganate multiplied by 0.491 gives 
the value in manganese." 

RED LEAD AND ORANGE MINERAL. 

" These pigments in the pure state are oxides of lead (approxi- 
mately Pb 3 4 ), being probably mixtures of compounds of varying 
proportions of lead monoxide and lead dioxide. Moisture, 
insoluble impurities, and total lead may be determined by the 
methods given under chrome yellow; or, in the absence of 
alkaline earth metals, the lead may be determined as sulphate 
in nitric acid solution (dissolve by adding a few drops of hydrogen 
dioxide) by evaporating with an excess of sulphuric acid until 
fumes of sulphuric anhydride are evolved. Determine as sulphate 
in the usual way. 

"The lead dioxide (Pb0 2 ) may be determined as follows: 
Weigh o . 5 gram of the very finely ground pigment into a 150 c.c. 



THE ANALYSIS OF DRY PIGMENTS. 29 

Erlenmeyer flask. Mix in a small beaker 15 grams of crystallized 
sodium acetate, 1.2 grams of potassium iodide, 5 c.c. of water, 
.and 5 c.c. of 50 per cent, acetic acid. Stir until all is liquid, pour 
into the Erlenmeyer flask containing the lead, and rub with a 
glass rod until all of the lead is dissolved; add 15 c.c. of water, 
and titrate with tenth-normal sodium thiosulphate, using starch 
as indicator. A small amount of lead may escape solution at 
first, but when the titration is nearly complete this may be 
dissolved by stirring. The reagents should be mixed in the 
order given, and the titration should be carried out as soon as 
the lead is in solution, as otherwise there is danger of loss of 
iodine. One cubic centimeter of tenth-normal sodium thio- 
sulphate corresponds to o. 01 1945 gram of lead dioxide, or 
0.034235 gram of red lead (Pb 3 4 ). 

" These colored lead pigments may have their color modified 
by the addition of organic coloring matters. As a general rule, 
such adulteration may be detected by adding 20 c.c. of 95 per 
cent, alcohol to -2 grams of the pigment, heating to a boil, and 
allowing to settle. Pour off the alcohol, boil with water, and 
allow to settle, then use very dilute ammonium hydroxide. If 
either the alcohol, water, or ammonium hydroxide is colored, 
it indicates organic coloring matter. The quantitative deter- 
mination of such adulteration is difficult and must generally be 
estimated by difference." 

Vermilion. 

" True vermilion, or, as it is generally called, English vermilion, 
is sulphide of mercury. On account of its cost it is rarely used 
in paints, and is liable to gross adulteration. It should show 
no bleeding on boiling with alcohol and water and no free sulphur 
by extraction with carbon disulphide. A small quantity mixed 
with five or six times its weight of dry sodium carbonate and 
heated in a tube should show globules of mercury on the cooler 
portion of the tube. The best test for purity is the ash, which 
should be not more than one-half of 1 per cent. Make the 
determination in a porcelain dish or crucible, using 2 grams of 
the sample. Ash in a muffle or in a hood with a very good draft, 
as the mercury fumes are very poisonous. It is seldom necessary 
to make a determination of the mercury; but if this is required, 



30 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

it may be determined by mixing 0.2 gram of the vermilion with 
o. 1 gram of very fine iron filings, or better "iron by hydrogen." 
Mix in a porcelain crucible and cover with a layer 10 mm. thick 
of the iron filings, place the crucible in a hole in an asbestos 
sheet so that it goes about half way through, cover with a 
weighed, well fitting, gold lid which is hollow at the top, fill 
this cavity with water, heat the crucible for fifteen minutes 
with a small flame, keep the cover filled with water, cool, remove 
the cover, dry for three minutes at 100 C, and thirty minutes 
in a desiccator, and weigh. The increase in weight is due to 
mercury. The mercury can be driven off from the gold by 
heating to about 450 C. A silver lid may be used, but gold is 
much better. 

" Another method is to place in the closed end of a combustion 
tube, 45 cm. long and 10 to 15 mm. in diameter, a layer of 25 to 
50 mm. of roughly pulverized magnesite, then a mixture of 
10 to 15 grams of the vermilion with four or five times its weight 
of lime, followed by 5 cm. of lime, and plug the tube with asbestos. 
Draw out the end of the tube and bend it over at an angle of 
about 6o°. Tap the tube so as to make a channel along the top, 
and place it in a combustion furnace with the bent neck down, 
resting with its end a little below some water in a small flask or 
beaker. Heat first the lime layer, and carry the heat back to 
the mixture of lime and pigment. When all the mercury has 
been driven off, heat the magnesite, and the evolved carbon 
dioxide will drive out the last of the mercury vapors. Collect 
the mercury in a globule, wash, dry, and weigh. 

" Genuine vermilion is at the present time little used in paints. 
Organic lakes are used for most of the brilliant red, scarlet, and 
vermilion shades. These organic coloring matters are some- 
times precipitated on red lead, orange mineral, or zinc oxide; 
but as a usual thing the base is barytes, whiting, or china clay. 
Paranitraniline red, a compound of diazotized parani tramline and 
beta-naphthol is largely employed; but a number of colors may 
be used. To test for red colors in such a lake the following 
method from Hall* may be of value, though other colors may 
be employed, which makes the table of only limited use. 

* "The Chemistry of Paints and Paint Vehicles," p. 29. 



THE ANALYSIS OF DRY PIGMENTS. 



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32 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

"It is well also to try the action of reducing and oxidizing 
agents such as stannous chloride, ferric chloride, etc. (See Zerr, 
Bestimmung von Teerfarbstoffen in Farblacken; also Schultz 
and Julius, A Systematic Survey of the Organic Coloring Mat- 
ters.) 

" Paranitraniline red is soluble in chloroform. It is also well 
to try the solvent action on different reds, of sodium carbonate, 
etc. The amount of organic pigment present in such reds is 
generally very small, and when it cannot be determined by 
ignition owing to the presence of lead, zinc, or carbonate, it is best 
determined by difference."* 

BLUE PIGMENTS. 

The only two blue pigments which come into great use in 
the paint trade are Ultramarine and Prussian blue. 

Ultramarine Blue. 

Ultramarine blue is formed by burning together silicates, 
aluminates, sulphur, charcoal, and soda. Although of indefinite 
composition, it is essentially a silicate and sulphide of sodium and 
aluminum. This compound may be identified by its evolution of 
hydrogen sulphide when treated with acid. Although seldom 
used in the paint trade, if an analysis is desired, it may be carried 
out in the following way. 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Silica. — One gram of the sample is digested with 20 c.c. 
dilute hydrochloric acid to complete decomposition, taking 
care to avoid spattering. Evaporate to dryness, dehydrate, 
cool, moisten with a few drops of concentrated hydrochloric acid. 
Repeat the evaporation and dehydration, cool, moisten with a 
few c.c. concentrated hydrochloric acid, dilute with hot water, 
filter, and weigh the insoluble residue. Treat the contents of 
the crucible with an excess of hydrofluoric acid and a few drops 
of sulphuric acid, evaporate to dryness, and ignite. The loss 
will be silica. Any residue remaining after this treatment should 
be examined. 

Alumina. — The filtrate from the silica is treated with ammo- 

* Bulletin 109, revised, Bureau of Chemistry, U. S. Dept. of Agri- 
culture, pp. 31, 32 and S3- 



THE ANALYSIS OF DRY PIGMENTS. 33 

■ 

nium hydroxide until faintly alkaline. The aluminum hy- 
droxide precipitated is filtered, washed, and weighed as A1 2 3 . 
If iron is present it may be separated from alumina by the 
fusion method as stated under the analysis of white pigments. 

Sodium Oxide. — Treat the filtrate after the removal of the 
aluminum with sulphuric acid until faintly acid. Evaporate 
to dryness, weigh the sodium sulphate in a weighed dish. Should 
calcium be present, the sodium is determined in the filtrate after 
the removal and determination of the calcium as oxalate, in the 
way previously stated. 

Total Sulphur. — One gram of the sample is fused with a mix- 
ture of potassium nitrate and sodium carbonate. Dissolve the 
fused mass in hydrochloric acid and boil, after the addition of 
concentrated nitric acid. Filter off the insoluble residue. Deter- 
mine the sulphate in the filtrate in the usual way, by precipita- 
tion as barium sulphate with barium chloride. The sodium 
peroxide method for the oxidation of sulphur is often used for 
this determination. 

Sulphur Present as Sulphate. — One gram of the sample is 
boiled with dilute hydrochloric acid until all the hydrogen 
sulphide has been driven off. Filter and wash the insoluble 
residue with hot water, precipitate the sulphur present in the 
filtrate, as usual. The amount of the sulphate present is deducted 
from the total sulphur found as sulphate by the fusion method, 
— the difference calculated to sulphur and reported as such. 

Ultramarine blues usually vary between the following limits: 

Sulphur, 10 to 14 per cent. 

Sulphur trioxide, 2 to 5 per cent. 

Alumina, 20 to 27 per cent. 

Silica, 39 to 45 per cent. 

Soda, 15 to 20 per cent. 

Prussian Blue (Antwerp Blue and Chinese Blue *) . 

This pigment is a double iron and potassium salt of hydro- 
ferricyanic and hydroferrocyanic acids. Its composition is rather 
indefinite and consequently analyses of the compound give varied 
results. The following method of analysis has been much used 
by the authors : 

* Chinese Blue often contains a small percentage of tin salts. They 
should be looked for in the qualitative examination. 

3 



! 



34 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

Moisture. — Two grams of the sample are heated at 105 C. 
for two hours. The loss will be moisture. Less than 7 per 
cent, moisture should be present in dry Prussian blue. 

Iron and Aluminum Oxides. — One gram of the sample is 
ignited at a low temperature until the last trace of blue has been 
decomposed. The ignition must be low, so as to prevent any- 
iron from being rendered difficultly soluble in hydrochloric 
acid. After cooling, treat the mass with 25 c.c. hydrochloric 
acid 1 : 1 and digest for one hour. No residue will remain if a 
pure Prussian blue is being examined. In some instances a resi- 
due does remain after this treatment, due to the presence of 
inert bases upon which the blue has been precipitated, such as 
barytes. Should such an insoluble residue be present, evaporate 
the solution to dryness, take up with hot water and dilute 
hydrochloric acid, boil, filter, wash, and weigh the insoluble resi- 
due. Examine this for silica, barium sulphate, and alumina. 

The filtrate from the last treatment, or the original solution, 
should no insoluble matter be present, is divided into aliquot 
portions. One of these portions is made faintly acid with 
ammonium hydroxide and the combined aluminum and iron 
hydroxides formed filtered, washed, and weighed in the usual 
way. The iron may be determined in the combined oxides 
by fusion with potassium acid sulphate and titration with 
potassium permanganate in the usual way. The filtrate should 
be examined for calcium present as calcium sulphate. 

Nitrogen. — Nitrogen is determined by the Kjehdahl-Gunning 
method. 

Commercial Method. — According to Parry and Coste,* the 
percentage of Prussian blue can be determined with sufficient 
accuracy for commercial purposes by multiplying the percentage 
of nitrogen by 4.4 and the percentage of iron by 3.03. The 
iron in this case may be titrated directly after solution in hydro- 
chloric acid. 

Akalies and Sulphuric Acid. — Alkaline salts are estimated 
in the filtrate after the removal of calcium, in the usual way 
One of them only will usually be present. Calculate to metal, 
then to sulphate, accounting for all the sulphuric acid as alka- 
line sulphate. 

Sulphuric acid is determined in the other aliquot portion, by 

* The Analyst, 1896, 21, 225 to 230. 



THE ANALYSIS OF DRY PIGMENTS. 35 

precipitation as barium sulphate, in the usual way. It is 
calculated to alkaline sulphate. 

Yellow and Orange Pigments (American Vermilion, Chrome 
Yellow, Lemon Chrome, and Orange Chrome). 

The above pigments, varying in color, always contain 
chromates. The light colored pigments usually contain lead 
sulphate or other insoluble lead compounds. The darker 
pigments sometimes contain basic lead chromate. It is advisable 
to treat the pigment with alcohol to determine the presence of 
any organic coloring matter. Pure chrome yellow should 
contain only lead chromate and insoluble lead compounds. 
These pigments are analyzed in the following way: 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. Loss will be moisture. 

Insoluble Residue. — One gram of the sample is treated with 
25 c.c. concentrated hydrochloric acid, the solution boiled, 
during which a few drops of alcohol are added one at a time. 
Dilute to 100 c.c. with hot water, continue the boiling for ten 
minutes, filter, wash, weigh the insoluble residue. This residue 
is examined for silica, barium sulphate, and alumina. 

Lead. — After neutralizing the greater portion of the acid 
present with ammonium hydroxide, after the removal of the 
insoluble residue, the solution is diluted to about 300 c.c. with 
water. Precipitate the lead completely with hydrogen sulphide, 
allow to settle, evaporate, wash with hydrogen sulphide water. 
Dissolve the lead sulphide in hot dilute nitric acid, add an 
excess of sulphuric acid, evaporate until heavy fumes of sul- 
phuric acid are given off, cool, dilute with water, add an equal 
volume of alcohol, filter, determine the lead either volumetrically 
or gravimetrically, as given under White Lead. 

Chromium. — The nitrate from the lead precipitate is boiled 
until all the hydrogen sulphide is expelled. Precipitate the 
chromium as chromium hydroxide with ammonium hydroxide, 
observing the usual precautions for preventing the precipitation 
of any zinc. Filter, wash, and weigh as chromic oxide. Cal- 
culate to chromic anhydride. 

Zinc. — Precipitate the zinc in the filtrate from the chromium 
precipitation, with hydrogen sulphide, as given under Zinc 



36 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

Oxide, filter, wash, and weigh. Determine the zinc either 
gravimetrically or volume trically, as before outlined. 

Calcium and Magnesium. — Determine the calcium and 
magnesium in the filtrate in the usual way. 

Sulphuric Acid. — The combined sulphate is estimated by 
dissolving i gram of the sample in hydrochloric acid, removing 
the insoluble residue by filtration, precipitating as barium 
sulphate, in the usual way. The barium sulphate precipitated 
will be pure, providing the solution is kept dilute and hot, 
otherwise lead sulphate may be precipitated. Should the 
precipitate become contaminated, the sulphate is best determined 
by the Hughes method, as outlined on page 17. 



GREEN PIGMENTS. 

(Chrome Green.) 

The green pigments which are of most importance are those 
consisting of a mixture of Prussian blue and chrome yellow. 
Organic colors are sometimes used to give the pigment a bright 
tint. It isr well to examine all green pigments for coloring mat- 
ter by boiling with alcohol. 

Owing to the various composition of greens, due to the method 
of manufacture, a chemical examination is attended with many 
difficulties, and in many cases is of small value in determining 
the true value of the green. The usual methods of color assay 
for strength, by mixing with a weighed portion of white-base 
pigment and observing the tint produced, should be made. 
The pigment should also be carefully examined by means of the 
microscope, so as to determine whether the green is a product 
made by precipitating the two pigments together or by mixing 
the blue and yellow pigments after separate precipitation. The 
former have the greater value. A good green will show the 
presence of green and blue particles but no yellow, while a poor 
green will show yellow and blue particles mixed with green. 
Analysis of the green may be made in the following way : 

Moisture. — Heat 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Insoluble Residue. — One gram of the sample is heated at a 
very low heat in a casserole until the blue color has been com- 



THE ANALYSIS OF DRY PIGMENTS. 37 

pletely destroyed, keeping the temperature sufficiently low so as 
not to render any of the iron or lead chromates insoluble. Cool, 
add 30 c.c. of concentrated hydrochloric acid, boil until all the 
soluble constituents have passed into solution. This can be 
hastened by the addition of a few drops of alcohol added one at 
a time. Dilute with water, boil, filter, wash, and weigh the 
insoluble residue. This residue is then carefully examined for 
silica, barytes, and occasionally alumina in the manner given 
under the analysis of a white pigment. 

Lead. — The excess of acid present in the filtrate from the in- 
soluble residue is neutralized with ammonia until barely acid. 
Dilute to 300 c.c, allow to cool, and treat with hydrogen sul- 
phide until the lead sulphide is completely precipitated. Allow 
the precipitate to settle, filter, wash, dissolve in nitric acid, 
determine the lead as described under the analysis of yellow 
pigments. 

Iron, Alumina, and Chromium. — The filtrate from the lead 
precipitate is boiled until all the hydrogen sulphide has been 
expelled. Add a few drops of nitric acid, boil for a few minutes 
to complete oxidation of the iron, precipitate the iron, alumina, * 
and chromium as hydroxides with ammonium hydroxide. 
This precipitate is filtered off, washed, and dissolved in hydro- 
chloric acid and made up to a definite volume. In one portion 
the iron, aluminum, and chromium hydroxides are precipitated 
with ammonium hydroxide, filtered, washed, and weighed to- 
gether. Another portion is treated in a flask with an excess of 
potassium hydroxide and bromine water until the iron hydroxide 
has assumed its characteristic reddish brown color. Dilute 
with water, filter, and wash. Dissolve the iron hydroxide in 
hydrochloric acid and determine the iron in the solution either 
volumetrically or gravimetrically, as stated under the analysis 
of iron oxides. The filtrate from the iron precipitate is made 
, acid with nitric acid, and the alumina precipitated and deter- 
mined in the usual way by precipitation with ammonium hy- 
droxide. Chromium is determined in the filtrate by reduction 
to a chromic salt -with hydrochloric acid and alcohol, precipitated 
with ammonium hydroxide and weighed as oxide. 

Calcium and Magnesium. — Calcium and magnesium are 
determined in the filtrate from the iron, alumina, and chromium 
precipitation. 



38 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

Sulphuric Acid. — One gram of the sample, after ignition until 
the blue is completely decomposed, as before stated, is dissolved 
in 30 c.c. of concentrated hydrochloric acid, diluted with water, 
boiled, filtered, and washed. Determine the barium sulphate 
in the usual way. 

Nitrogen. — Nitrogen is determined as stated under the 
analysis of Prussian blue. 

Interpretations of Results. — The Prussian blue present is 
determined by multiplying the iron found by 3 . 03 or the nitro- 
gen found by 4.4. The sulphate is calculated to lead sulphate 
and calcium sulphate, should calcium be present, and the 
chromium to lead chromate. 

BLACK PIGMENTS (Bone Black, Drop Black, Ivory Black, 

Lampblack, Mineral Black, Graphite). 

The usual black pigments are those consisting of carbon, 
existing either in the crystalline form (graphite) or the amorphous 
form which includes all the many artificial carbon blacks. Many 
paints are made at the present time from coal-tar and asphaltic 
mixtures, and it is deemed advisable to treat of these, owing to 
many difficulties attending their analysis, under a separate chap- 
ter. For the analysis of simple black pigments the following 
method will be found to embrace all the essential points needed 
for their examination. An extraction of the black pigment 
should be made with ether to determine the presence of oil. 
If present, it may be determined gravimetrically in a fat extrac- 
tion apparatus. 

Moisture. — Dry 2 grams of the sample at 105 C. for two 
hours. Loss will be moisture. 

Volatile Matter. — One gram of the sample is heated in a large 
covered crucible with a Bunsen burner for ten minutes. The 
loss will be volatile matter. 

Ash. — Two grams of the sample are ignited at a bright red 
heat until the carbon has all been driven off. The residue will 
be ash. Should the black pigment consist of graphite, the 
ignition must be made with the aid of oxygen. Ignite until all 
the carbon is burned off and report as carbon. Should carbonates 
be present, the ash is mixed with a small amount of ammonium 
carbonate and again ignited and weighed. This will reconvert 



THE ANALYSIS OF DRY PIGMENTS. 39 

any carbonates which may have been converted to oxides on 
ignition. 

Soluble Salts. — The ash from the above is boiled with con- 
centrated hydrochloric acid, diluted with water, again boiled, 
filtered, and the insoluble residue weighed. Should it be 
desired, the insoluble residue may be examined for silica, barium 
sulphate, and alumina. The nitrate is examined for phosphoric 
acid, calcium, and magnesium. 



■ 



CHAPTER II. 
THE ANALYSIS OF MIXED PIGMENTS AND PAINTS. 

After making the usual observations as to the statements on 
the label of the can, gross weight of package, etc., the can is 
opened, and the material well stirred, preferably by transferring 
the entire contents to a large receptacle. A uniform sample is 
then withdrawn for analysis. The original can may be cali- 
brated by pouring in a standard volume of water. 

A portion (about 15 grams) of the sample of paint withdrawn 
for analysis is weighed into a 2 -ounce tared centrifuge bottle, 
and 40 c.c. of a vehicle solvent* added. The bottle is then 
capped and placed in the centrifuge machine for twenty minutes, 
when it is removed and the vehicle poured off from the settled 
pigment. Successive portions of solvent are again added, and 
the operation repeated several times until the pigment has been 
thoroughly extracted. The bottle and its contents of pigment 
is dried at 105 C. in an air-bath, and, after weighing, the loss is 
calculated to the percentage of vehicle in the paint, the balance 
being, of course, pigment. 

The dried pigment is now ready for analysis. 

GENERAL METHODS FOR THE ANALYSIS OF A MIXED 

WHITE PAINT. 

Any of the constituents mentioned under the analysis of 
simple white pigments may be present in a mixed white paint. 
The analysis may be considerably shortened by a preliminary 
qualitative examination. It is assumed, however, that zinc sul- 
phide will not be present with lead compounds, as such a mixture 
is apt to blacken. Either of the following general methods may 
be used in such an analysis. 

Method 1. — One gram of the dry pigment is treated with 20 
c.c. (1:1) hydrochloric acid. Evaporate to dryness, moisten 
with a few cubic centimeters of concentrated hydrochloric acid, 

* 50 parts benzol, 40 parts wood alcohol, 10 parts acetone. 

40 



THE ANALYSIS OF MIXED PIGMENTS AND PAINTS. 41 

allow to stand for several minutes, dilute to 100 c.c. with hot 
water, boil, filter, and wash the insoluble residue with hot water. 
It is advisable to treat the residue after washing into the original 
beaker with 1 : 1 hydrochloric acid and 2 c.c. of dilute sulphuric 
acid. Boil, filter and wash. This will usually remove the last 
traces of lead. Should no barium sulphate be present, the 
hydrochloric acid-sulphuric acid treatment may be used in the 
first instance. The insoluble residue is ignited and weighed. 
After weighing, treat the contents of the crucible with an excess 
of hydrofluoric acid and a few drops of sulphuric acid. Evapo- 
rate to dryness and ignite. The loss will be silica. 

The residue, after the silica has been removed by volatiliza- 
tion, is fused with potassium acid sulphate, and the melt taken 
up in hot water. Filter, wash, and weigh, as given under Barium 
Sulphate. The nitrates from the original fusion and extraction 
are then combined. A sodium carbonate fusion may also be 
resorted to in place of potassium acid sulphate at this point. 

Warm the combined filtrates and pass in hydrogen sulphide 
until the lead is completely precipitated, having from 3 to 4 1 1 2 
c.c. of concentrated hydrochloric acid for every 100 c.c. of neu- 
tral solution. If the color of this precipitate is gray, it is a 
sign that some zinc is being precipitated, and acid must be 
added. Should the precipitate be reddish-black, the solution 
is too acid. Cool the contents of the beaker, filter, and wash. 
The lead is estimated as described under Basic Carbonate White 
Lead. Boil the filtrate from the lead precipitate until the hy- 
drogen sulphide is completely removed. Add a few drops of 
nitric acid, ammonium chloride, and ammonium hydroxide to 
faint excess. Filter, wash, and weigh the aluminum oxide and 
any iron oxide which is precipitated in the usual way, observing 
the usual precautions to prevent the precipitation of zinc. 
Should the residue be colored, indicating the presence of iron, 
the iron oxide may be separated from the alumina by fusion 
with potassium acid sulphate. Take up the fusion with water, 
acidify with sulphuric acid, reduce with zinc, and titrate in the 
usual way with potassium permanganate. Calculate to Fe 2 3 . 
The difference between this and the total oxides will be A1 2 3 . 
The amount of iron oxide present in the case of white pigments 
will be in most cases inappreciable. Acidify the filtrate from 
the iron oxide and alumina faintly with acetic acid and heat to 



42 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

boiling. Saturate with H 2 S and boil for ten minutes. Deter- 
mine the zinc either gravimetrically or volumetrically, as under 
Zinc Oxide. To the bo ling alkaline filtrate add boiling ammon- 
ium oxalate, and determine the calcium in the usual way. Pre- 
cipitate the magnesium in the filtrate with sodium hydrogen 
phosphate and determine in the usual way. 

Barium carbonate is sometimes found in mixed paints, and 
it is well to test for this before the precipitation of calcium. A 
relatively large percentage of magnesium denotes the presence of 
asbestine. 

The calculation of aluminum oxide to clay and determination 
of the silica present is carried out, according to Scott, as follows: 

Weight of Al 2 O s X2 . 5372 = Weight of clay. 
Weight of Clay X . 4667 = Weight of Si0 2 in clay. 

Any difference greater than 5 per cent, may be considered 
silica. 

Estimation of S0 4 in the lead sulphate which may be present. 
Treat 1 gram of the sample with 200 c.c. of water and dilute 
hydrochloric acid. Add several pieces of spongy zinc and boil. 
After complete precipitation of the lead, filter and wash. Pre- 
cipitate the sulphuric acid in the usual way, as barium sulphate. 
Filter, wash, and weigh. Calculate the S0 4 to lead sulphate. 

Method 2. — The second method depends upon the sepa- 
ration of the compounds soluble in acetic acid from the in- 
soluble compounds. 

Moisture. — Dry 2 grams of the sample at 105 C. for two 
hours. The loss will be moisture. 

Residue Insoluble in Acetic Acid. — One gram of the sample 
is boiled with a mixture of 10 c.c. 95 per cent, acetic acid and 
25 c.c. of water. Filter and wash the insoluble residue. The 
filtrate is carefully preserved for quantitative examination. 
The insoluble residue, after washing into a beaker, is treated with 
25 c.c. of hydrochloric acid (1.2) and 5 grams of ammonium 
chloride. Heat on the steam-bath for a few minutes, dilute 
with hot water to about 300 c.c, boil, filter, wash, and weigh 
the insoluble residue. This residue is examined for silica, 
aluminum, and barium sulphate, as stated under the first method 
for the general analysis of pigments. The lead is precipitated 
in the filtrate in the usual way with hydrogen sulphide. The 



THE ANALYSIS OF MIXED PIGMENTS AND PAINTS. 43 

lead sulphide precipitate is filtered, washed, dissolved in nitric 
acid, evaporated in the presence of sulphuric acid, and deter- 
mined either gravimetrically or volume trically, as stated under 
Basic Carbonate- White Lead. The lead found is calculated to 
lead sulphate. The filtrate from the lead precipitate is examined 
for aluminum and calcium in the usual way. Any calcium is 
calculated to calcium sulphate. 

Compounds Soluble in Acetic Acid. — The filtrate from the 
acetic acid treatment may contain lead, zinc, barium, calcium 
and magnesium. The zinc and lead are removed by passing 
hydrogen sulphide into the hot solution until completely pre- 
cipitated. Filter, wash, dissolve in nitric acid, evaporate in the 
presence of sulphuric acid, and determine the lead, as before 
stated. Calculate to basic carbonate of lead. The zinc is 
determined in the filtrate from the lead either gravimetrically 
or volume trically, as stated under Zinc Oxide. Calculate to zinc 
oxide. The filtrate from the lead and zinc precipitate, after 
removal of the hydrogen sulphide by boiling, is examined for 
barium, calcium, and magnesium, as stated in the first method 
for the analysis of white pigments. Calculate to carbonates. 

The total sulphate present, both soluble and insoluble, can 
best be determined by the method as outlined under the analysis 
of zinc lead and leaded zinc. 

Should the qualitative examination of the mixed pigment 
show definitely its composition, recourse can be had to such 
shortened methods as given by Thompson.* 

"Sample 1 is a mixture of barytes, white lead, and zinc 
oxide. 

"Two 1 -gram portions are weighed out. One is dissolved 
in acetic acid and filtered, the insoluble matter ignited and 
weighed as barytes, the lead in the soluble portion precipitated 
with bichromate of potash, weighed in Gooch crucible as chro- 
mate, and calculated to white lead. 

"The other portion is dissolved in dilute nitric acid, sul- 
phuric acid added in excess, evaporation carried to fumes, water 
added, the zinc sulphate solution filtered from barytes and lead 
sulphate and precipitated directly as carbonate, filtered, ignited, 
and weighed as oxide. 

* J. Soc.£hem. Ind., June 30, 1896, Vol. XV, No. 6, pp. 433, 434. 



1 

J 



44 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

"Sample 2 is a mixture of barytes and so-called sublimed 
white lead. 

" Weigh out three i-gram portions. In one determine zinc 
oxide as in Case 1 . Treat a second portion with boiling acetic 
acid, filter, determine lead in filtrate and calculate to lead oxide. 
Treat third portion by boiling with acid ammonium acetate, 
filter, ignite, and weigh residue as barytes, determine total 
lead in filtrate, deduct from it the lead as oxide, and calculate 
the remainder to sulphate. Sublimed lead contains no hydrate 
of lead, and its relative whiteness is probably due to the oxide 
of lead being combined with the sulphate as basic sulphate. 
Its analysis should be reported in terms of sulphate of lead, 
oxide of lead, and oxide of zinc. 

" Sample 3 is a mixture of barytes, sublimed lead, and white 
lead. 

" Determine barytes, zinc oxide, lead soluble in acetic acid 
and in ammonium acetate, as in Case 2 ; also determine carbonic 
acid, which calculate to white lead, deduct lead in white lead 
from the lead soluble in acetic acid, and calculate the remainder 
to lead oxide. 

" Sample 4 is a mixture of barytes, white lead, and carbonate 
of lime. 

" Determine barytes and lead soluble in acetic acid (white 
lead) as in Case 1. In filtrate from lead chromate precipitate 
lime as oxalate, weigh as sulphate, and calculate to carbonate. 
Chromic acid does not interfere with the precipitation of lime 
as oxalate from acetic acid solution. 

"Sample 5 is a mixture of barytes, white lead, zinc oxide, 
and carbonate of lime. 

"Determine barytes and white lead as in Case 1. Dissolve 
another portion in acetic acid, filter and pass sulphuretted 
hydrogen through the boiling solution, filter, and precipitate 
lime in filtrate as oxalate; dissolve mixed sulphides of lead and 
zinc in dilute nitric acid, evaporate to fumes with sulphuric 
acid, separate, and determine zinc oxide as in Case 1. 

" Sample 6 is a mixture of barytes, white lead, sublimed lead, 
and carbonate of lime. 

" Determine barytes, lead soluble in acetic acid and in am- 
monium acetate, as in Case 2, lime and zinc oxide, as in Case 5, 
and carbonic acid. Calculate lime to carbonate of lime, deduct 



THE ANALYSIS OF MIXED PIGMENTS AND PAINTS. 45 

carbonic acid in it from total carbonic acid, calculate the re- 
mainder of it to white lead, deduct lead in white lead from lead 
soluble in acetic acid, and calculate the remainder to oxide of 
lead. 

" Sample 7 contains sulphate of lime. 

11 Analysis of paints containing sulphate of lime present 
peculiar difficulties from its proneness to give up sulphuric acid 
to lead oxide or white lead if present. Sulphate of lime and 
white lead boiled in water are more or less mutually decomposed 
with the formation of sulphate of lead and carbonate of lime. 
A method for the determination of sulphate of lime is by pro- 
longed washing with water with slight suction in a weighed 
Gooch crucible. This is exceedingly tedious, but thoroughly 
accurate. A reservoir containing water may be placed above 
the crucible, and the water allowed to drop slowly into it. This 
may take one or two days to bring the sample to constant 
weight, during which time several liters of water will have 
passed through the crucible. Another method for separating 
the sulphate of lime is by treatment in a weighed Gooch crucible 
with a mixture of nine parts of 95 per cent, alcohol and one part 
of glacial acetic acid. Acetates of lead, zinc, and lime being 
soluble in this mixture, the residue contains all the sulphate of 
lime and any sulphate of lead and barytes which may be present. 
Determine the lead and lime as in sample 4, and calculate to 
sulphates. Sulphate of lime should be fully hydrated in paints. 
To determine this, obtain loss on ignition; deduct carbonic 
acid and water in other constituents; the remainder should agree 
fairly well with the calculated water in the hydrated sulphate 
of lime, if it is fully hydrated. If, after washing a small portion 
pi the sample with water, the residue shows no sulphuric acid 
soluble in ammonium acetate, the sulphate of lime may be 
obtained by determining the sulphuric acid soluble in ammonium 
acetate and calculating to sulphate of lime. The difficulty 
is in determining the sulphate of lime in the presence, or possible 
presence, of sulphate, of lead. To illustrate the analysis of 
samples of white paint containing sulphate of lime and the 
difficulty attending thereon, we would mention a sample con- 
taining sublimed lead, white lead, carbonate of lime, and sulphate 
of lime. In such a sample we would determine the lead, lime, 
sulphuric acid, carbonic acid, loss on ignition, the portion soluble 



• 



46 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

in water, and the lime or sulphuric acid in that portion, cal 
culating to sulphate of lime. Deduct the lime in the sulphate 
of lime from the total lime, and calculate the remainder to 
carbonate of lime; deduct the carbonic acid in the carbonate 
of lime from the total carbonic acid, and calculate the remainder 
to white lead; deduct the sulphuric acid in the sulphate of lime 
from the total sulphuric acid, and calculate the remainder to 
sulphate of lead. The lead unaccounted for as sulphate or white 
lead is present as oxide of lead. Deduct the carbonic acid and 
water in the carbonate of lime and white lead from the loss on 
ignition, the remainder being the water of hydration of the 
sulphate of lime. 

11 Sample 8 contains as insoluble matter, barytes, china clay, 
and silica. 

" After igniting and weighing the insoluble matter, carbonate 
of soda is added to it, and the mixture fused. The fused mass 
is treated with water, and the insoluble portion filtered off and 
washed. This insoluble portion is dissolved in dilute hydro- ' 

chloric acid, and the barium present precipitated with sulphuric 
acid in excess. The barium sulphate is filtered out, ignited, 
weighed, and if this weight does not differ materially — say by 
2 per cent. — from the weight of the total insoluble matter, the 
total insoluble matter is reported as barytes. If the difference 
is greater than this, add the filtrate from the barium sulphate 
precipitate to the water-soluble portion of fusion. Evaporate 
and determine the silica and the alumina in the regular way. 
Calculate the alumina to China clay on the arbitrary formula 
2Si0 2 , A1 2 3 , 2H 2 0, and deduct the silica in it from the -total 
silica, reporting the latter in a free states It is to be borne in 
mind that china clay gives a loss of about 13 per cent, on igni- 
tion, which must be allowed for. China clay is but slightly used 
in white paints as compared with barytes and silica.' ' 
' "Sample 9 contains sulphide of zinc. 

"Samples of this character are usually mixtures in varying 
proportions of barium sulphate, sulphide of zinc, and oxide of 
zinc. Determine barytes as matter insoluble in nitric acid, the 
total zinc as in Case 1, and the zinc soluble in acetic acid, which 
is oxide of zinc. Calculate the zinc insoluble in acetic acid to 
sulphide." 

"Sample 10 contains sulphite of lead. 



THE ANALYSIS OF MIXED PIGMENTS AND PAINTS. 47 

"This is of rare occurrence. Sulphite of lead is insoluble 
in ammonium acetate, and may be filtered out and weighed as 
such. It is apt on exposure to the air in the moist state to be- 
come oxidized to sulphate of lead. 

"There are certain arbitrary positions which the chemist 
must take in reporting analyses of white paints: 

"First. — White lead is not uniformly of the composition 
usually given as theoretical (2PbC0 3 ), (PbH 2 2 ), but in report- 
ing we must accept this as the basis of calculating results, 
unless it is demonstrated that the composition of the white 
lead is very abnormal. 

"Second. — In reporting oxide of lead present this should not 
be done except in the presence of sulphate of lead, and if white 
lead is present, then only where the oxide is more than 1 per cent. ; 
otherwise calculate all the lead soluble in acetic acid to white 
lead. , 

" Third. — China clay is to be calculated to the arbitrary for- 
mula given. 

"In outlining the above methods we have in mind many 
samples that we have analyzed, and the combinations we have 
chosen are those we have actually found present/ ' 

General Methods for the Analysis of a Mixed Colored Paint. — 
Such a paint may contain any of the constituents mentioned 
under the various colored pigments. A qualitative examination 
of the paint will reveal the composition of the color present, 
and the constituents of such a color are then determined as spe- 
cifically stated under the analysis of that particular colored pig- 
ment. The general analysis of the pigment, excepting that of 
the coloring portion, is carried out as stated under the analysis 
of a mixed white paint. 



CHAPTER III. 
ANALYSIS OF PAINT VEHICLES AND VARNISHES. 

The can of paint is allowed to stand until the pigment has 
thoroughly settled, leaving the vehicle floating on top. A 
quantity of this separated vehicle is then removed from the can 
and carefully preserved in an air-tight bottle, after determining 
its specific gravity. A weighed portion of the vehicle may then 
be placed in a tared flask and attached to a Liebig condenser. 
Heating to 200 C. will drive off the volatile constituents. The 
composition of the distillate may be determined by following 
the methods outlined elsewhere. The residue (oil, drier and 
gums) may be transferred to a crucible and ignited. The 
residue from the ignition may then be weighed and calculated 
to ash. An analysis of this ash for lead, manganese and other 
driers, may then be proceeded with in the usual manner. 

When a paint is very thick and will not settle so that the 
analyst cannot secure a good sample of the vehicle, a weighed 
portion of the paint may be placed in the thimble of a Soxhlet 
extractor and extraction of the vehicle made in the usual manner, 
with a known amount of solvent. 

Some operators prefer to take a weighed quantity of the paint, 
as it comes from the can, say, 100 grams, and place it in a copper 
flask, mixing it thoroughly therein with sand. Distillation of 
this mass will drive over the water and volatile constituents 
which will separate in two distinct layers in the graduate in 
which they are collected. For the separation of very fine pig- 
ments, such as certain colors in oil, a Gooch crucible * is useful : 
Successive extractions of the pigment are decanted through a 
carefully prepared Gooch crucible, using a heavy bed of very 
fine asbestos, with a fairly strong suction. 

Water. — Leo Nemzek of the North Dakota Agricultural Col- 
lege, who has had a wide experience in the analysis of paint, 

♦Warren I. Keeler, Jour. Indus, and Engineer. Chem., Vol. 2, No. 9, 
p. 388. 

48 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 49 

recommends the following method for the determination of 
water in ready-mixed paint: 

Weigh out 100 grams of the paint into a 300 c.c. Erlenmeyer 
flask, and heat gradually after having added about 75 c.c. of 
toluol. The heat should not exceed 105 C. Distil over about 
50 c.c. and read percentage of water. This method does not 
take in the water which such pigments as white lead carbonate, 
calcium sulphate, etc., give up at 150 C. 

LINSEED OIL. 

A good linseed oil will analyze within the following limits, 
as the results of several samples analyzed by the authors show: 

Specific gravity at 15.5° C, .932 to .935 

Acid number, 5 to 7 

Saponification value, 187 to 192 

Unsaponifiable matter, . 8 to 1.5% 

* Iodine number, 180 to 190 

The analytical methods outlined by Walkerf are most 
excellent. Close adherence to these methods have given 
satisfactory results on a long series of tests conducted by the 
authors. 

» 

1. Preparation of Sample. 

" All tests are to be made on oil which has been filtered through 
paper at a temperature of between 15 and 30 C. immediately 
before weighing, with the exception of tests No. 6, Turbidity; 
No. 7, Foots; No. 9, Moisture- and Volatile Matter, and No. 10, 
Ash. The sample should be thoroughly agitated before the 
removal of a portion for filtration or analysis. 

2. Specific Gravity. 

"Determine with a pyknometer, plummet, or hydrometer 
at 15. 5 C. 

3. Viscosity. 

" Use the Engler-Ubbelohde method, making the determina- 
tion at 20 C. 

* (May sometimes be as low as 160.) 

t P. H. Walker, Some Technical Methods of Testing Miscellaneous 
Supplies, Bulletin No. 109, revised, Bureau of Chemistry, U. S. Dept. 
of Agriculture, 1910, pp. 11, 12 and 13. 

4 



/ 



56 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

4. Flash Point, Open Cup. 

" Set a nickel crucible 60 mm. in diameter at the top, 40 mm. 
in diameter at the bottom, and 60 mm. in height in a hole in the 
middle of a sheet of asbestos board 200 mm. square. The bottom 
of the crucible should project about 25 mm. through the asbestos. 
Support the asbestos on a tripod and suspend a thermometer 
reading to 400 C. in degrees in the center of the crucible, so that 
the lower end of the thermometer is 10 mm. from the bottom 
of the crucible. Then pour in the oil until its level is 15 mm. 
below the top of the crucible. Place a Bunsen burner below 
the crucible and regulate the size of flame so that the thermome- 
ter rises 9 a minute. As a test flame use an ordinary blowpipe 
attached -toa gas tube. The flame should be about 6 mm. long. 
Begin testing when the temperature of the oil reaches 220 C, 
and test for every rise of 3 . In applying the test move the 
flame slowly across the entire width of the crucible immediately 
in front of the thermometer and 10 mm. above the surface of the 
oil. The flask point is the lowest temperature at which the 
vapors above the oil flash and then go out. 

5. Fire Point. 

" After noting the temperature at which the oil flashes con- 
tinue the heating until the vapors catch fire and burn over the 
surface of the oil. The temperature at which this takes place 
is the fire point. In determining the flash point note the 
behavior of the oil. It should not foam or crack on heating. 
Foaming and cracking are frequently caused by the presence of 
water. 

6. Turbidity. 
" Note whether the oil is perfectly clear or not. 

7. Foots. 

" Let a liter of the oil stand in a clear glass bottle for eight 
days, and then note the amount of sediment formed. The 
highest grades of oil show no turbidity or foots by this test. 
The claim is made that sometimes what would be called foots 
by the above method is due to the freezing out of fats of rather 
high melting point. When a sufficient amount of the sample is 
available, heat one portion to ioo° C. and set it aside for the 



\> 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 5 1 

determination of foots, together with a sample just as it is 
received. Note also the odor of the warm oil, rubbing it on the 
hands; a small amount of fish oil may be detected in this way. 

8. Break. 

" Heat 50 c.c. of the oil in a beaker to 300 C. Note whether 
the oil remains unchanged or " breaks ;" that is, shows clots of a 
jelly-like consistency. 

9. Moisture and Volatile Matter. 

" Heat about 5 grams of oil in an oven at 105 for forty-five 
minutes; the loss in weight is considered as moisture. This de- 
termination is of course not exact, as there is some oxidation. 
When a more accurate determination is desired, perform the 
whole operation in an atmosphere of hydrogen. 

10. Ash. 

" Burn about 20 grams of oil in a porcelain dish and conduct 
the ashing at as low a temperature as possible. The best oil 
should contain only a trace of ash. An amount as large as o. 2 
per cent, would indicate an adulterated or boiled oil. Examine 
the ash for lead, manganese, and calcium. 

11. Drying on Glass. 

" Coat glass plates 3 by 4 inches with the oils to be examined, 
expose to air and light, and note when the film ceases to be tacky. 
A good oil should dry to an elastic coherent film in three days. 
Varying conditions of light, temperature, and moisture have 
such an influence on drying tests that for comparison of one 
linseed oil with others all samples must be run at the same time. 

12. Drying on Lead Monoxide. 

" Livache's test calls for precipitated lead, but litharge gives 
equally good results. Spread about 5 grams of litharge over 
the flat bottom of an aluminum dish 2 . 5 inches in diameter and 
5/8 inch high; weigh the dish and the litharge; distribute as 
evenly as possible over the litharge 0.5 to o . 7 gram of the oil, 
weigh exactly, expose to the air and light for ninety-six hours, 
weigh again, and calculate the gain in weight to percentage based 
on the original weight of the oil used. 



52 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

13. Acid Number. 

"Weigh 10 grams of oil in a 200 c.c. Erlenmeyer flask, add 50 
c.c. of neutral alcohol, connect with a reflux air condenser, and 
heat on a steam bath for half an hour. Remove from the bath, 
cool, add phenolphthalein, and titrate the free acid with fifth- 
normal sodium hydroxide. Calculate as the acid number (milli- 
grams of potassium hydroxide to 1 gram of oil) . The acid num- 
ber varies with the age of the oil, and should be less than 8, 
though when the oil is refined with sulphuric acid it may show 
a higher acid number. Test for sulphuric acid. 

14. Saponification Number. 

"Weigh from 2 to 3 grams of oil in a 200 c.c. Erlenmeyer 
flask, add 30 c.c. of a half -normal alcoholic solution of potassium 
hydroxide, connect with a reflux air condenser, heat on a steam 
bath for an hour, then titrate with half-normal sulphuric acid, 
using phenolphthalein as indicator. Always run two blanks 
with the alcoholic potash. From the difference between the 
number of cubic centimeters of acid required by the blanks and 
the determinations, calculate the saponification number (milli- 
grams of potassium hydroxide to 1 gram of oil) . The saponifica- 
tion number should be about 190. 

15. Unsaponifiable Matter. 

"As the saponification varies somewhat in pure oil, it is 
sometimes advisable to make a direct determination of unsaponi- 
fiable matter. Saponify from 5 to 10 grams of oil with alcoholic 
potassium hydroxide (200 c.c. of a half -normal solution) for an 
hour on a steam bath, using a reflux condenser. Then remove 
the condenser and evaporate the alcohol as completely as possible; 
dissolve the soap in 75 c.c. of water, transfer to a separatory 
funnel, cool, shake out with two portions of 50 c.c. each of 
gasoline distilled between 35 and 50 C, wash the gasoline twice 
with water, evaporate the gasoline, and weigh the unsaponifiable 
matter, which in raw linseed oil should be below 1 . 5 per cent. ; in 
boiled oil it is somewhat higher, but should be below 2 . 5 per cent. 

16. Iodine Number. 

" Weigh in a small glass capsule from 0.2 to o. 25 gram of oil, 
transfer to a 350 c.c. bottle having a well-ground stopper; 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 53 

dissolve the oil in 10 c.c. of chloroform and add 30 c.c. of Hanus 
solution; let it stand with occasional shaking for one hour, add 
20 c.c. of a 10 per cent, solution of potassium iodide and 150 c.c. 
of water, and titrate with standard sodium thiosulphate, using 
starch as indicator. Blanks must be run each time. From 
the difference between the amounts of sodium thiosulphate 
required by the blanks and the determination, calculate the 
iodine number (centigrams of iodine to 1 gram of oil) . The iodine 
number of raw linseed oil varies from 175 to 193, though Gill 
states that a pure raw oil may give a value as low as 160. Boiled 
oil may be very much lower. 

" Make the Hanus solution by dissolving 13.2 grams of iodine 
in 1,000 c.c. of glacial acetic acid which will not reduce chromic 
acid, and adding 3 c.c. of bromine. 

17. Rosin or Rosin Oil (Liebermann -Store h Test). 

"To 20 grams of oil add 50 c.c. of alcohol, heat on a steam 
bath for fifteen minutes, cool, decant the alcohol, evaporate to 
dryness, add 5 c.c. of acetic anhydride, warm, cool, draw off 
the acetic anhydride, and add a drop of sulphuric acid, 1 . 53 
specific gravity. Rosin or rosin oil gives a fugitive violet' color." 

The hexabromide test is sometimes of value. The method 
used by Committee E in their work on linseed oil follows :* 

"Hexabromide Test. — On oil, determining the melting point 
of the bromide compounds. Method to be followed: The 
determination should be made in glass-stoppered^Hhlrin'ng 
bottles, about 6 inches high and 1 inch in diameter, wrarflat 
bottom, and weighing about 30 grams each. These bottles 
should be carefully dried and weighed. Weigh into one of these 
bottles 0.3 gram of oil to be tested; add 25 c.c. of absolute ether; 
cool to near o° C; add bromine, drop by drop, until a con- 
siderable excess is shown by the color of the solution. Stir 
constantly during this addition, and add bromine very slowly 
to avoid heating. Place tube in ice water for thirty minutes; 
then in centrifuge, whirling for two minutes at speed of 1,200 
revolutions per minute. This throws the brominated oil to 
the bottom of the tube, from which the supernatant liquid can 
be easily and quickly decanted. Add 10 c.c. of cold ether; 
stir precipitate with glass rod; allow to stand in ice water until 

* Proc. Amer. Soc. for Testing Materials, Vol. IX, p. 152. 



54 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

thoroughly cold. Whirl in centrifuge again, and decant super- 
natant liquor. Another washing in the same manner will 
remove the excess of bromine and oil. Allow the tube and 
residue to stand for a short time, until the ether has evaporated ; 
dry in water bath for thirty minutes, and weigh (Tolman's 
method)." 

Acetyl Value. 

The determination of acetyl value is based on the principle 
that hydroxy acids on being heated with acetic anhydride 
exchange the hydrogen atom of their hydroxy group or groups 
for the radicle of acetic acid. The procedure is as follows: 

Boil the oil with an equal volume of acetic anhydride for 
two hours in a round-bottomed flask attached to an inverted 
condenser, transfer to a large beaker, mix with several hundred 
cubic centimeters of water and boil for half an hour. 

A slow current of C0 2 should be passed into the liquid 
through a finely drawn-out tube reaching nearly to the bottom 
of the beaker; this is done to prevent bumping. The mixture 
is allowed to separate into two layers, the water is siphoned off 
and the oily layer again boiled out until the last trace of acetic 
acid is removed, which can be ascertained by testing with litmus 
paper. The acetylated product is freed from water and finally 
filtered through filter-paper in a drying oven. 

*"This operation may be carried out quantitatively, and in 
that case the washing is best done on a weighed filter. On 
weighing the acetylated oil or fat, an increase of weight would 
prove that assimilation of acetyl groups has taken place. This 
method may be found useful to ascertain preliminarily whether 
a notable amount of hydroxylated acids is present in the sample 
under examination. 

"Two or 4 grams of the acetylated substance are saponified 
by means of alcoholic potash solution, as in the determination 
of the saponification value. If the ' distillation process' be 
adopted it is not necessary to work with an accurately measured 
quantity of standardized alcoholic potash. In case the 'filtra- 
tion process' be used, the alcoholic potash must be measured 
exactly. (It is, however, advisable to employ in either case a 

♦Commercial Organic Analysis, by Alfred H. Allen, pp. 66 and 67. 
P. Blakiston's Son & Co., Philadelphia, 1905. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 55 

known volume of standard alkali, as one is then enabled to 
determine the saponification value of the acetylated oil or fat.) 
Next the alcohol is evaporated and the soap dissolved in water. 
From this stage the determination is carried out either by the 
(a) 'distillation process* or (b) 'filtration process.' 

"(a) Distillation Process. — Add dilute sulphuric acid (1:10), 
more than sufficient to saturate the potash, and distil as usual 
in Reichert's distillation process. Since several 100 c.c. must be 
distilled off, either a current of steam is blown through the sus- 
pended fatty acids or water is run into the distilling flask, from 
time to time, through a stoppered funnel fixed in the cork, or any 
other convenient device is adopted. It will be found quite suffi- 
cient to distil over 500 to 700 c.c, as the last 100 c.c. contain 
practically no acid. Filter the distillates to remove any insoluble 
acids carried over by the steam, anc^itrate the filtrates with 
decinormal potash, phenolphthalein bei^ the indicator. Multiply 
the number of cubic centimeters by 5.61 and divide the product 
by the weight of substance taken. This gives the acetyl value. 

" (b) Filtration Process. — Add to the soap solution a quantity 
of standardized sulphuric acid exactly corresponding to the 
amount of alcoholic potash employed and warm gently, when 
the fatty acids will readily collect on the top as an oily layer. 
(If the saponification value has been determined it is, of course, 
necessary to take into account the volume of acid used for 
titrating back the excess of potash.) Filter off the liberated 
fatty acids, wash with boiling water until the washings are no 
longer acid, and titrate the filtrate with decinormal potash, 
using phenolphthalein as indicator. The acetyl value is cal- 
culated in the manner shown above. 

"Both methods give identical results; the latter will be 
found shorter. 

"The acetyl value indicates the number of milligrams of 
KOH required for the neutralization of the acetic acid obtained 
on saponifying 1 gram of the acetylated fat or wax." 

Maumene Test. 

While this test is not strictly a quantitative one, the indica- 
tions afforded by it are of considerable value. It depends on the 
heat developed by the mixing of the oil with strong sulphuric 
acid and is carried out as follows : 



56 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

A beaker of about 150 c.c. capacity and from 7 1/2 to 9 cm. 
deep is carefully placed into a larger vessel and surrounded with 
dry felt or cotton waste. 

Fifty grams of the oil are put into the beaker and 10 c.c. of 
concentrated sulphuric acid are gradually introduced into the 
oil from a burette and the mixture stirred until no further in- 
crease in temperature is recorded by a thermometer immersed 
in it. 

The highest point at which the thermometer remains con- 
stant for any appreciable time is observed, and the difference be- 
tween this and the initial temperature is the rise of temperature. 

In performing this test, it is highly important that the oil 
and acid be originally of the same temperature and that the 
strength of the acid should be the same as far as possible. 

As the rise in temperature varies with the strength of the 
acid, to secure uniformity the results should be expressed by 
dividing the rise of temperature with the oil by the rise of 
temperature with water and multiplying by 100. This is called 
the specific temperature reaction. 

The rise of temperature with water is determined in the same 
manner as with oil, using the same vessel. 

Raw linseed oil gives a Maumend number about 20 F. in 
excess of that given by some boiled linseed oils. 

Polarimetric Test for Rosin Oil with Linseed Oil. 

*"The investigations of Bishop and Peters on the opticity 
of a number of oils show that, with the exception of caster oil, 
croton oil and rosin oil, the only dextrorotations are produced by 
sesame (high) and olive oil (feeble), all the others, including 
linseed oil, being either optically inactive or having a light levo- 
rotatory power. 

"(1) The Polarimetric Examination of Linseed Oil Sophisti- 
cated with Refined Rosin Oil (R. R. O.). — According to Aignan 
such a mixture rotates the plane of polarization to the right by 
an angle perceptibly proportional to the quantity of rosin oil 
which it contains. If the rotation observed with a 200 mm. tube 
be represented by a D and the weight of the rosin oil in 100 

♦The Manufacture of Varnishes, and Kindred Industries, Livache 
and Mcintosh, Vol. I, D. Van Nostrand Company, New York, 1904. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 57 

parts by weight of the mixture by h, we get in the case of a mix- 
ture of linseed oil with 

1. Refined rosin oil, [a] D + =14/15 h. 

2. Choice white rosin oil, [aj D 4- =17/15 h. 

3. Rectified rosin oil, [a] D + =21/15 n - 

"The first mixture is the most common. In actual practice, 
therefore, all that has to be done is to measure a D by the polar- 
i meter, and to estimate h as refined rosin oil, according to the 
formula h=[aJD 15/14. The oils in question being dark in 
color, it is better to work in a 100 mm. tube and to calculate 

h=[a]D=i 5 /7. 

" (2) Estimation of Rosin Oil in Paint by the Polarimeter. — (A) 
A certain amount of the paint is frequently stirred and shaken 
up with ether and allowed to settle. The ether containing the 
oil in solution floats to the surface and the polarization tube is 
filled with the ethereal solution. If no optical deviation be 
produced, there is no rosin oil in the paint tested. On the other 
hand, if [a]D be the rotation toward the right with a 200 mm. 
tube, according to Aignan's researches on the rotatory power 
of an ethereal solution of linseed oil containing rosin oil, the 
proportion of rosin oil may be calculated by the formula 

a[D] 

h== " 2* 

43 2 

" (B) A known weight, p 1 , of the ethereal solution is run into 

a flask and heated on the water-bath at 100 C. (212 F.) so as 

to drive off the ether; the oil which boils only at 300 C. (57 2 ° F.) 

is left in the flask. Let its weight be represented by p 2 . The 

proportion— - 100 =h x per cent, of oil (linseed oil and rosin oil) 
p2 

contained in the ethereal solution examined by the polarimeter. 
If h 1 =h, it may be taken for granted that the paint contained 
linseed oil free from rosin oil. Generally, h 1 is greater than h, 

then — -100 will give the percentage of rosin oil contained in 
h 1 

the linseed oil which was used to make the paint.' ' 

.The detection of other vegetable or animal oil, admixed with 

linseed oil, is not always an easy task when they are present in 

small percentage. Petroleum oil and rosin oil are the most 



58 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

common adulterants. The detection and estimation of the 
former is given on page 52. 

The presence of rosin oil as an adulterant may be detected 
by shaking the oil with an equal quantity of acetic anhydride. 
Acetic anhydride is removed from the oil and mixed with a few 
drops of concentrated sulphuric acid. Production of a violet 
color indicates the presence of a rosin oil. Its specific gravity 
is very high and saponification number very low. 

Lewkowitsch* shows the determination of rosin acids in 
admixture with fatty acids, as follows : 

"Twitchell's method is based on the property aliphatic 
acids possess of being converted into their ethylic esters when 
acted upon by hydrochloric acid gas in their alcoholic solution, 
whereas colophony practically undergoes little change under 
the same treatment, abietic acid separating from the solution. 
The analysis is carried out as follows: 

" Two to three grams of the mixed fatty and rosin acids are 
weighed off accurately, dissolved in a flask in ten times their 
volume of absolute alcohol (90 per cent, alcohol must not be used, 
as the conversion of fatty acids into esters is not complete in 
that case), and a current of dry hydrochloric acid gas passed 
through, the flask being cooled by immersion in cold water. 
The gas is rapidly absorbed at first, and after about forty-five 
minutes, when unabsorbed gas is noticed to escape, the operation 
is finished. To ensure complete esterification the flask is allowed 
to stand for an hour, during which time the ethylic esters and 
the rosin acids separate on the top as an oily layer. The con- 
tents of the flask are then diluted with five times their volume 
of water, and boiled until the aqueous solution has become clear. 
From this stage the analysis may be carried out either (a) 
volumetrically or (b) gravimetrically. 

" (a) The Volumetric Analysis — The contents of the flask 
are transferred to a separating funnel, and the flask rinsed out 
several times with ether. After vigorous shaking the acid 
layer is run off, and the remaining ethereal solution, containing 
the ethylic esters and the rosin acids, washed with water until 
the last trace of hydrochloric acid is removed. Fifty c.c. of 
alcohol are then added, and the solution titrated with standard 

* Chemical Technology and Analysis of Oils, Fats, and Waxes, 
by Lewkowitsch, Vol. I, p. 394. The Macmillan Co., New York, 1904. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 59 

caustic potash or soda, using phenolphthalein as an indicator. 
The rosin acids combine at once with the alkali, whereas the 
ethylic esters remain practically unaltered. Adopting as the 
combining equivalent for rosin 346, the number of c.c. of normal 
alkali used multiplied by o . 346 will give the amount of rosin in 
the sample. 

" (b) The Gravimetric Method. — The contents of the flask 
are mixed with a little petroleum ether, boiling below 8o° C, 
and transferred to a separating funnel, the flask being washed 
out with the same solvent. The petroleum ether layer should 
measure about 50 c.c. After shaking, the acid solution is run 
off, and the petroleum ether layer washed once with water, and 
then treated in the funnel with a solution of 0.5 grm. potassium 
hydroxide and 5 c.c. of alcohol in 50 c.c. of water. The ethylic 
esters dissolved in the petroleum ether will then be found to float 
on the top, the rosin acids having been extracted by the dilute 
alkaline solution to form rosin soap. The soap solution is 
then run off, decomposed with hydrochloric acid, and the 
separated rosin acids collected as such, or preferably dissolved 
in ether and isolated after evaporating the ether. The residue, 
dried and weighed, gives the amount of rosin in the sample/ ' 

The detection of olive oil, palm oil, cocoanut oil, cotton-seed 
oil, fish oil, and other vegetable and animal oils may be made 
by following the methods in "Oil Analysis/ ' by Gill (Lippincott 
Co.). The low iodine values of the above-named oils as com- 
pared to that of linseed oil is generally sufficient evidence of 
their presence. 

SOYA BEAN OIL. 

Soya bean oil in its chemical constants runs so close to lin- 
seed oil that it is very hard to detect. The same methods can be 
used, however, as for the analysis of linseed oil. When working 
upon mixtures of the two the following table of the authors will 
probably be valuable in their identification. 



6o 



ANALYSIS OF PAINTS AND PAINTING MATERIALS, 



Chemical Characteristics Of Soya Bean Oil. 



Sample 

No. | 

l 


Specific 
gravity 

.0.9233 
0.924 

0.9231 

0.9233 


Acid 
No. 

1.87 
1 .92 
1.90 
1. 91 


Saponifica- 
tion No. 

188.4 
188.3 
187.8 
188.4 


Iodine 
No. 

127.8 
127.2 

131. 7 
129.8 

130.0 

132.6 

136.0 


Per cent, 
of foots. 


i 

2 

3 
4 

5 
6 


3.81 










7 










/ 










Average . . 


0.9234 


1.90 


188.2 


130.7 





It is evident that the iodine value of soya bean oil is the only- 
chemical characteristic that markedly differentiates it from 
linseed oil. Therefore, in the detection of soya bean oil and its 
estimation, the iodine values of several samples of mixed oils are 
given as being of interest in this connection: 



Iodine Values Of Linseed Oil And Mixed Oils. 



Sample 
No. 


Straight 
linseed 

190.3 

189.5 
188.0 


25% soya. 
75% linseed 

1752 

175.9 
175-4 


50% soya. 
50% linseed 


75% s °ya. 
25% linseed 


" 


1 
2 

3 


160.7 
161. 7 
160.3 


140.4 
140.8 

139.9 


Average .... 


189.3 


175-5 

_ 


160.9 

• 


140.4 



The authors have found that treatment of a few drops of 
soya bean oil, or oil containing any considerable percentage of 
soya bean oil, with one drop of concentrated sulphuric acid will 
produce a distinct fluorescent yellowish-green color. This 
color is entirely different from that produced with pure linseed 
oil, which is of a brownish-red and of a begonia-shaped pattern. 
This test is best conducted on the lid of a porcelain crucible. 
Subsequent examination under the microscope is of value in 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 6l 

confirming the test. The comparatively slow drying of soya 
bean oil will often indicate its presence. 

CHINESE WOOD OIL. 

Investigations, extending over several years, conducted by 
Kreikenbaum,* determined that Chinese wood oil as it comes 
to the paint trade is fairly uniform in its constants. Kreiken- 
baum's work also determined that the Hanus method for the 
determination of the iodine number, although applicable in 
the case of linseed oil, could not be used when working on 
Chinese wood oil, as it gave abnormally high results. The 
average constants of a large number of commercial samples 
determined by Kreikenbaum follow: 



Specific gravity 


.941 to .943 


Free acid, 


4.4 


Saponification number, 


190.9 


Hubl iodine number, 


169 to 171 



Working with the Hubl method a six-hour absorption is 
sufficient to get good accurate results when determining the 
iodine number of this oil. 

SPIRITS OF TURPENTINE, PETROLEUM AND LIGHT OILS. 

For a quick test to determine whether a turpentine is pure, 
the chemist may mix in a test-tube 10 c.c. of the material under 
examination and 10 c.c. of aniline oil. If the turpentine is pure, 
the two materials will mix without turbidity. If petroleum 
products are present, they will be indicated by a cloudiness and 
quick separation in a distinct layer from the turpentine and 
aniline oil. 

The following methods have been given by Walkerf for the 
analysis of the volatile solvents used to a great extent in the 
manufacture of paints: 

* Adolph Kreikenbaum. Constants of Chinese Wood Oil, Vol. II, 
No. 5, Jour. Indus, and Engineer. Chem. 

*(• P. H. Walker. Some Technical Methods of Testing Miscellaneous 
Supplies, Bull. 109, revised, Bureau of Chemistry, U. S. Dept. of 
Agriculture, 1910, pp. 13, 14, and 15. 



62 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

SPIRITS OF TURPENTINE.* 

i. Color. 

"The best quality of spirits of turpentine should be water- 
white. 

2. Specific Gravity. 

" Determine the specific gravity with a pyknometer, plum- 
met, or hydrometer at 15 . 5 C. Pure gum turpentine should have 
a density between 0.862 and 0.875. Wood turpentine may, 
however, range from o. 860 to 0.910 or even higher. 

3. Distillation. 

"Connect a distilling flask of 150 c.c. capacity with a con- 
denser having a thermometer. Introduce 100 c.c. of turpentine 
and heat with a Bunsen burner. The initial boiling point should 
be about 156 C, and 95 per cent, should distil over between 
153-5° and 165. 5 C. 

4. Residue on Evaporation. 

"Evaporate 10 grams on the steam-bath; the residue should 
be less than 2 per cent. 

5. Refractive Index. 

" Determine with a Zeiss direct reading refractometer at 20 C. 
The index of refraction for gum turpentine should be from 
1 . 4690 to 1 . 4740; for wood turpentine, 1 . 4685 to 1 . 5150. 

6. Action of Sulphuric Acid (Polymerization). 

" Measure 6 c.c. of turpentine in a stoppered, thin-walled 
tube graduated to 0.1 c.c. (carbon tubes). Place the tube in 
cold water and pour in slowly a mixture of four parts of strong 
sulphuric acid and one part of fuming sulphuric acid. Add 
the acid slowly, and avoid an excessive rise in temperature. 
Shake the tube so as to mix the turpentine and the acid, add 
finally about 20 c.c. of the acid, stopper the tube, mix thoroughly, 
cool, allow to stand thirty minutes, and note the volume of un- 
polymerized oil that collects on top of the acid layer. Then 

* If wood turpentine has been carefully refined, it will comply with 
all the tests given for spirits of turpentine, but it can almost invariably 
be distinguished from the latter by its characteristic odor. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 63 

let stand for eighteen hours and again note the volume. A 
pure turpentine should show less than 0.3 c.c. unpolymerized 
at the end of thirty minutes, and less than 0.5 c.c. after eighteen 
hours. 

"This method will indicate gross* adulteration, but will not 
detect admixtures of very small amounts of mineral oil. Donk 
has perfected a method which determines the presence of as little 
as 1 per cent, of mineral oil in turpentine. This method is as 
follows : 

"Sulphuric acid of thirty-eight times the normal strength 
(101.5 per cent.) is prepared by mixing very strong sulphuric 
acid with fuming sulphuric acid. It must be determined by 
titration that this reagent is of the exact strength required, for 
with 37.5 times normal afeid (100 per cent.) the turpentine is not 
completely destroyed, and with acid stronger than 101 . 5 per cent, 
the amount of mineral oil dissolved becomes excessive. 

"Place about 25 c.c. of the special sulphuric acid in a flask 
having a narrow graduated neck (a Babcock bottle does very 
well), cool in ice-water, add 5 c.c. of the turpentine to be tested 
and cool the flask again, shaking it carefully and avoiding any 
excessive rise in temperature by frequent cooling. The flask 
should never be too hot to hold in the palm of the hand. Then 
place it in a bath of cold water and heat the bath at such a rate 
that in about five minutes the temperature will be 65 C. Dur- 
ing the heating shake the bottle about every fifty seconds, finally 
shaking very thoroughly so as to insure the contact of every 
particle of the sample with the acid. Cool to room temperature 
and add ordinary strong sulphuric acid in sufficient amount to 
bring the unpolymerized liquid up in the graduated neck. Let 
stand overnight or whirl in a centrifuge and read the volume on 
the neck. 

"Pure turpentine should leave a residue of not over 0.04 c.c, 
which is not limpid and which has a refractive index of not less 
than 1 . 500. 

"If the unpolymerized residue is 0.04 c.c. or less, mineral 
oil may be assumed to be absent. If the residue is greater, 
calculate from it the percentage of mineral oil present. This 
will be, of course, only approximate, for there is some residue 
from pure turpentine and some mineral oil is dissolved by the 
acid; but for all practical purposes it may be assumed that 



64 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

the errors balance one another, and hence it is not advisable to 
apply any correction. 

7. Spot Test. 

"Place a drop on filter-paper and allow it to dry at room 
temperature; it should leave no stain. 

8. Flash Point. 

" Support a crucible, such as is used in determining the flash 
point of linseed oil, in a vessel of water at 15 to 20 C; the 
water should cover about two-thirds of the crucible. Fill the 
crucible to within about 2 cm. of the top with turpentine, insert 
a thermometer, and heat the water bath slowly, i° per minute. 
Begin at 37 and test for the flash at each rise of 0.5 . The 
turpentine should not flash under 40. 5 C. 

Wood Turpentine. 

The steam method* for the distillation of wood turpentine, 
as worked up by Geer, Bristol, Hawley, and others of the Forest 
Products Laboratory of the United States, separates the various 
high and low boiling-point fractions, all of which have different 
characteristics. 

BENZINE AND LIGHT PETROLEUM OILS. 

"The term benzine is used for a number of light petroleum 
oils. In the painting trade it generally refers to a product of 
about 62 Baum6 (0.7292 sp. gr.). The petroleum benzine 
of the U. S. Pharmacopoeia is a lighter oil, being a light gasoline. 

1. Specific Gravity. 

" Determine with a spindle, pyknometer, or plummet at 
I 5-5° C. The determination can be made at room temperature 
and corrected to 15.5 C. 

2. Sulphur (Sodium Nitroprusside Test). 

"To 100 c.c. of the sample in a flask add about 1 gram of 
bright "metallic sodium, connect with a reflux condenser, and 
boil for one hour. Cool, add water drop by drop until the metal 

* The Analysis of Turpentine by Fractional Distillation with Steam , 
by Wm. C. Geer, U. S. Dept. of Agriculture, Forest Service Circular 
152. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 65 

is dissolved, separate the aqueous liquid, and test with a drop of 
sodium nitroprusside solution. A fine violet-blue coloration 
indicates sulphur. 

3. Sulphur Compounds and Pyrogenous Products (U. S. P. Test). 

"To 100 c.c. of the sample add 25 c.c. of a solution of 10 per 
cent, anhydrous ammonia in 95 per cent, alcohol (spirit of am- 
monia U. S. P.), add 1 c.c. of silver nitrate solution. Boil 
gently for five minutes. A brown coloration indicates sulphur 
compounds or pyrogenous products. 

4. Residue on Evaporation. 

"Place 25 c.c. in a 100 c.c. platinum dish, heat on steam-bath 
for thirty minutes, and weigh residue. No residue should be 
left by this test. 

5. Fractional Distillation. 

"Light petroleum oils are usually tested only for specific 
gravity; but as light and heavy distillates may be mixed, the 
specifications would be improved by requiring that a certain 
fraction should distil between specified temperatures. To 
make this determination distil 100 c.c. in a round-bottom flask 
6.5 cm. in diameter; the neck should be 1.6 cm. in diameter 
and 15 cm. long, with a side tube set in the middle of the neck 
at an angle of 75 . The surface of the liquid should be 9 cm. 
below the side tube, and the bulb of the thermometer just below 
the side tube. 

6. Benzol. 

" Mix the sample with 8 volumes of strong sulphuric acid and 
2 volumes of nitric acid; heat gently for ten minutes, allow to 
cool, and note odor. The odor of nitrobenzol indicates benzol. 

7. Color and Odor. 

"Note color of sample and odor both in bulk and after 
rubbing on hands." 

ANALYSIS OF VARNISH AND JAPAN. 

An examination of a varnish should be largely of a physical 
nature, the chemist determining its appearance, odor, body, 
clarity, and properties of the dried film. The specific gravity, 

5 



66 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

flash point, viscosity, acid number, ash, and rosin test, as well 
as the percentage of volatile oils, are determined in the usual 
manner, as outlined for linseed oil on previous pages. The 
percentage of fixed oils and gums is determined by weighing 
that portion left in the flask after distillation of the volatile 
constituents. Owing to the chemical combinations and changes 
which are effected when various gums are heated together in 
the presence of oils, it is almost impossible for the most expert 
analyst to determine the exact make-up of a varnish. The 
analyst, however, may determine the total percentage of gums 
and the percentage total of oils with a fair degree of accuracy, 
on an original sample by precipitation of the insoluble gums 
with gasoline, determining the soluble gums in the benzine by 
extraction with chloroform after evaporation of the gasoline 
and oxidation of the oil. To make an exact determination of a 
varnish formula, however, as it was submitted to the varnish 
maker, is almost impossible. 

Oils, Gums and Volatile. — In ordinary varnish which gen- 
erally contains oil, gums and volatile solvents like benzine and 
terpentine, weigh off 10 grams into a tall thin beaker of 400 c.c. 
capacity. Next add a large amount of ice cold petroleum ether. 
Cover the beaker and allow to stand for several hours when the 
gums will be found separated at the bottom of the beaker. 
Repeat the extraction with cold petroleum ether at least three 
times, pouring the several decanted portions into a large bottle. 

After finishing the extraction, add 100 c.c. of ice cold water 
to the petroleum ether in the bottle and shake thoroughly, 
causing a small amount of gum which usually dissolves in the 
ether to reprecipitate. Filter on a tared filter, previously 
moistened with ice water, and also transfer to this filter the gum 
contained in the beaker, using a stirring rod and some petroleum 
ether to loosen' it from the glass, washing finally with a small 
quantity of ice water. Dry at 100 C. and weigh as gums. 

If the oil is also to be determined, the petroleum ether and 
water can be separated in a separatory funnel and the ether 
then evaporated or distilled off, leaving the oil. 

The sum of the oil and gums subtracted from 100 gives the 
percentage of volatile thinners — benzine, turpentine, etc. 

Distillation of the volatile solvents from a separate portion 
of the varnish may be used to determine the percentage of 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 67 

turpentine by the polymerization method previously outlined 
in this chapter. 

In spirit varnishes, like shellac, to determine the gums it is 
only necessary to weigh off 10 grams into a tared porcelain dish 
and evaporate off the solvent on the water bath. 

Mcllhiney's method for the analysis of oil varnishes has been 
used by the authors with success. This method may also be 
used in the analysis of japan driers. 

Mcllhiney's Method. — Of the materials used in construction 
few if any present more difficult problems in their testing and 
analysis than oil varnishes. Any rational system of testing 
varnishes to determine their suitability for a given use and 
their resistance to the destructive effects of exposure to the 
elements, will take account among other tests of a chemical 
analysis to determine the ingredients of the varnish and the 
proportions in which they are combined. It is unfortunate that 
there is not at the present time any method of analysis which 
will determine with any reasonable degree of accuracy, the 
proportions in which the oil, hard gum, and common rosin 
have been combined to form the nonvolatile base from which the 
varnish is produced by dilution with turpentine or other volatile 
oil. The proportion of volatile oil in the varnish may be deter- 
mined by distilling the solvent off with steam at a temperature 
a little above the boiling point of water and then separating the 
volatile oil from the aqueous part of the distillate and weighing 
or measuring it. Its further examination need not be entered 
upon here since methods of analysis of such volatile oils as are 
likely to be used as thinners for varnish are now generally 
known and are described at length in such standard works as 
Allen's Commercial Organic Analysis, and the books on paints 
and varnishes by Toch, Sabin, and Holley and Ladd. 

The separation of the hard gum from the oil and the common 
rosin is the problem which is difficult; the hard gum and the oil 
do not unite at all, practically, until the hard gum has been 
melted and from 15 to 25 per cent, of its weight driven off as 
vapor, the amount so lost depending upon the character of the 
gum. After this melting the linseed oil may be added if it has 
been previously heated enough to prevent it from chilling the 
melted gum. This mixture of oil and gum is usually at this 



68 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

stage heated for a shorter or longer time to complete the com- 
bination of the ingredients. The union of oil and hard gum 
which has been effected by this means cannot be broken up 
by any solvent, or perhaps it would be more accurate to say 
that after the combination between hard gum and oil has been 
successfully made and the mixture thinned with turpentine 
and stored for a few months, no solvent can be depended upon 
regularly to effect a separation of the two by its selective solvent 
action. 

The process which is here described depends upon the fact 
that although the union between oil and hard gum is too intimate 
to be broken up by the selective solvent action of any solvent 
acting directly upon the original mixture, the combination may 
be broken up and the oil and gum brought back to more nearly 
their original condition before they were melted together, by 
submitting the mixture to the action of caustic potash in alcoholic 
solution and subsequently acidifying the solution of potash 
salts so formed. By this means there is obtained from hard 
gum varnishes a quantity of gum insoluble in petrolic ether 
very closely approximating the amount of hard gum actually 
existing in the varnishes, while the linseed oil is represented 
by its fatty acids which are readily soluble in this solvent unless 
they have been oxidized, in which case some of the fatty acids 
of the linseed oil will accompany the insoluble hard gum. 

In carrying out the method an opportunity is given to 
determine not only the weight of the oil and of gum but also the 
Koettstorfer figure and the percentage of glycerine in the 
mixture. All these data taken together give a basis for cor- 
roborating the main figures. 

The process is carried out by weighing into an Erlenmeyer 
flask 2 to 10 grams of the varnish, adding a considerable excess of 
approximately half-normal solution of caustic soda or caustic 
potash in very strong or absolute alcohol, distilling off the major 
portion of the solvent and redissolving in neutral absolute 
alcohol. The solution is then titrated with a solution of pure 
acetic acid in absolute alcohol, approximately half-normal 
strength, to determine the amount of the excess of alkali present. 
From this the Koettstorfer figure is determined as the exact 
strengths of the acid and alkali solutions have been ascertained 
independently by comparison with known standards. A 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 69 

further quantity of the standard solution of acid in alcohol is 
added so as to exactly neutralize the total amount of alkali 
originally added. By this means the acid bodies liberated 
from their combinations with alkali are obtained in solution in 
strong alcohol. To this solution there is now added a sufficient 
quantity of petrolic ether to dissolve the oil acids and this 
petrolic ether being miscible with the strong alcohol forms 
with it a homogeneous liquid. Water is now added to the 
mixture in such amount as to so dilute the alcohol contained 
that it is no longer a solvent for fatty or resin acids; this addition 
of water causes the petrolic ether which was mixed with the 
alcoholic liquid to separate carrying with it the fatty acids. 
The rosin goes with the fatty acids while the hard gum being 
insoluble in either the petrolic ether or in the very dilute alcohol 
separates in the solid state. The aqueous and ethereal layers 
are now separated in a separating funnel and each is washed, 
the watery layer with petrolic ether and the petrolic ether layer 
with water. The petrolic ether layer is now transferred to a 
weighed flask, the solvent distilled off, and the residue of fatty 
acids and common rosin weighed. This latter is then examined 
further by TwitcheH's method to determine the amount of rosin 
which it contains or it may be examined qualitatively in a 
number of ways to establish its identity. 

The aqueous layer is freed from the suspended hard gum 
which it contains by filtering, and from any further quantity 
of gum which the weak alcohol may have retained in solution by 
evaporating off the alcohol and again filtering. The remaining 
aqueous liquid contains the glycerin and this is determined by the 
Hehner method with potassium bichromate — the method ordi- 
narily used for examining spent soap lyes. 

The hard gum is, according to this plan, precipitated in such a 
way that it adheres to the sides of the glass vessel in which the 
alcohol and petrolic ether mixture is diluted with water; the 
easiest method to weigh it is, therefore, to carry on the operation 
of dilution in a weighed glass vessel and then to dry and weigh 
the hard gum in this vessel. It frequently happens that some 
of the hard gum cannot be conveniently retained in this vessel 
but that it must be filtered out on a weighed filter and the 
weight so found added to that of the main portion. 

If the varnish contains nonvolatile petroleum or other 



70 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

unsaponifiable matter it will naturally be included in the fatty 
and resin acids, and it would be necessary to saponify the latter 
and extract the unsaponifiable matter from them while in the 
alkaline state; this operation is so familiar to chemists that it is 
mentioned here only to call attention to the necessity for it in 
some cases. 

It would naturally be expected that on account of the well 
known insolubility of the oxidized fatty acids in petrolic ether, 
some of the acids of the linseed oil which had been polymerized 
by heat during the cooking of the varnish, or which had been 
oxidized during the blowing process to which some linseed oil is 
subjected before making it up into varnish, would fail to dissolve 
and would be counted in with the hard gum instead of with the 
linseed oil. It appears as a matter of fact that this source of 
error is of slight importance in the case of oil thickened by heat 
but that the blowing process gives an oil which is not com- 
pletely accounted for by the soluble fatty acids recovered. 
This difficulty may be largely overcome by taking advantage 
of the greater solubility of the oxidized fatty acids in alcohol 
as compared with the hard gum; the freshly precipitated gum 
contaminated with oxidized fatty acids is treated with a moder- 
ate quantity of cold alcohol of about 85 per cent, and allowed 
to digest for some time. The soluble matter so extracted is 
then recovered separately by evaporating off the alcohol. 

The great variety of hard gums in use and in the methods of 
making them up into varnish make the problem one of great 
complexity. It is not to be expected that any one method of 
analysis or any single set of directions for carrying on the 
operation of making the analysis would be generally applicable, 
and it is not the intention in this paper to give such detailed 
instructions. The method described has, however, been found 
to give, upon samples of known composition made up under 
conditions which imitate closely the conditions of practice in an 
ordinary varnish factory, results that were accurate to within 
reasonable limits. 

Rosin when present is usually combined with lime in the 
proportion of about one part of lime to twenty parts of rosin. 
An examination of the mineral constituents of the varnish is 
therefore of some value; the extraction of the mineral bases 
may be effected by treating a quantity of the varnish somewhat 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 7 1 

thinned with benzine, with strong hydrochloric acid, and 
examining the aqueous liquid. 

The amount of fatty acids obtained represents about 92.5 
per cent, of the linseed oil. The identification of these fatty 
acids as belonging to linseed oil or to china wood oil may be 
satisfactorily accomplished in some cases, but there are undoubt- 
edly many varnishes in which the analyst will be unable* to 
identify and determine the oils. The identification of the hard 
gums after separation from the other constituents of the varnish 
is a matter for which no rule can be given. The odor and 
physical characteristics of the recovered gum are quite as 
important as the known chemical tests of which the acidity 
and the Koettstorfer figure are among the most important. 
The chemistry of these gums is as yet almost unknown, but in the 
near future it is likely that our knowledge both of the nature of 
these hard gums and of methods for separating them from the 
other ingredients of the varnishes of which they form a part, 
will be very greatly increased. 

For the analysis of gums, the analyst is referred to Vols. I 
and II of Lewkowitsch, and to Allen's Commercial Organic 
Chemistry. The following method of Mcllhiney's for the 
analysis of shellac, being of such great value, is presented at this 
place : 

THE ANALYSIS OF SHELLAC. 

Mcllhiney's Method.* — In the last few years the analytical 
examination of shellac has become much more common because 
the users of shellac and the dealers in it have become better 
informed as to the extent to which adulteration has been prac- 
tised in the past, and particularly because more accurate and 
reliable methods of analysis have been devised for examining 
shellac. The most important adulterant of shellac, in fact 
almost the only adulterant, is common rosin or colophony, and 
it is to the detection and estimation of this adulterant that most 
of the analytical methods have been directed. The price of 
commercial shellac is determined by its color, freedom from dirt, 
etc., as well as by its content of colophony, but the chemist 
is not usually called upon to determine the commercial grade 

* Presented before the International Congress of Applied Chemistry. 



72 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

of shellac in other respects than its purity or freedom from 
adulteration. 

The methods which have been used with greater or less suc- 
cess to determine the amount of rosin in shellac depend first 
upon the different behavior of shellac and of colophony toward 
alkali; shellac when dissolved in alcohol is capable of neutralizing 
a much smaller amount of caustic soda or potash than rosin when 
under similar conditions, and tests based upon this property are 
used and are of some value particularly as corroborating the 
results of other tests. The difference, however, between shellac 
and rosin in this respect is not sufficiently marked nor are the 
various grades of pure shellac or of rosin sufficiently constant 
in their behavior when tested by such methods to furnish a 
fairly satisfactory method of analysis. (See Allen, Commercial 
Organic Analysis, Vol. II, Part 3, pp. 190-195.) 

Another property of rosin which has been used to distinguish 
and determine it in admixture with shellac is the solubility in 
ether of its compound or salt of rosin with silver while the similar 
compound of silver with shellac acids remain undissolved. The 
neutral constituents of shellac, that is, those which generally 
unite with either soda or silver are, however, also soluble in ether 
and are likely to be obtained in admixture with the rosin so 
that this method of analysis is objectionable. 

Shellac and rosin when treated with proper solutions of iodine 
behave very differently; the shellac absorbs a relatively small 
amount, varying from 7 to 18 per cent, of its weight of iodine, 
the amount depending upon the details of the process used, while 
rosin under similar conditions absorbs from 120 to 230 per cent, 
of its weight of iodine. For many years it was the practice to 
use for the examination of shellac in this way the Hubl process 
in which the iodine and the rosin to be tested are used in solution 
in alcohol to which a little chloroform has been added. This 
Hubl process was originally designed for the examination of 
fats and oils and although it was in its day a very useful process 
it has in recent years been replaced by others which are more 
rapid and accurate. 

The process which has been for the past few years in most 
common use in the United States for the determination of rosin 
in shellac is the iodine process which was originally suggested 
for use upon fats and oils by Wijs and which was later studied 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 73 

and adapted for use upon shellac by Langmuir and was finally 
recommended by the Sub-committee on Shellac Analysis of the 
American Chemical Society in Journal of American Chemical 
Society, XXIX, 122 1 to 1227, as the most reliable of those in use 
up to that time. The process consists in brief of the following 
steps: in a treatment of a fixed amount, 200 milligrams of the 
shellac to be tested dissolved in 20 c.c. of acetic acid of 99 per 
cent, strength to which 10 c.c. of chloroform is added, with 20 
c.c. of a solution of iodine monochloride in acetic acid of 99 per 
cent, strength for exactly one hour at a temperature of 21 to 
2 4 C. The amount of iodine which is absorbed under these 
conditions by rosin is assumed to be 228 per cent, of the weight 
of the rosin while shellac absorbs less than 18 per cent, of its 
weight and in making the calculation the iodine figure of the 
shellac is assumed to be 18. This process has given excellent 
results in practice particularly as it is capable of giving in the 
hands of different operators closely agreeing results upon the 
same sample. The objections to the use of this process are 
first that it is likely to give results below the truth and second 
that the method of ascertaining the amounts of rosin is an indirect 
one and any other substance having a high iodine figure would be 
counted as rosin; the rosin itself is at no stage of the process sepa- 
rated from the shellac and submitted to a separate examination. 
The need of a process of analysis which would actually 
separate the rosin from the shellac so that it can be examined 
by itself has led the writer to devise a process which has recently 
begun to be used in which the rosin is so separated from the 
shellac. This process which was described at length in the 
"Journal American Chemical Society, " XXX, 867 to 872, depends 
upon the fact that rosin is soluble in petrolic ether while shellac 
is not. Although it is not practicable to extract the rosin from 
solid shellac with petrolic ether, the latter may be used to separate 
the two resins when they are dissolved in a suitable solvent. The 
shellac to be examined is in this process dissolved in absolute 
alcohol or in glacial acetic acid; with both of these solvents 
petrolic ether is miscible. It is, therefore, added to the solution 
of the rosin, and to the resulting mixture water is added. This 
results in a separation of the alcoholic and petrolic ether layers 
as the diluted alcohol is no longer miscible with the petrolic 
ether. The petrolic ether carries with it the rosin, the wax 



74 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

contained in the shellac, providing sufficient petrolic ether was 
used to dissolve it, and traces of shellac or of some constituent 
of shellac. Several methods of separating the shellac wax from 
the rosin may be used, but the most convenient is to extract the 
petrolic ether solution of the two with an alkaline solution which 
removes the rosin and leaves the wax dissolved in the petrolic 
ether. From the alkaline solution of the rosin the latter may be 
recovered by acidifying, extracting the acidified solution with a 
solvent such as ether and distilling off the ether to obtain the 
rosin which may then be weighed. 

After considerable experience with this method the following , 
details as to mode of procedure ha\re been found convenient as 
well as tending to give accurate results. Place 2 grams of the 
shellac to be examined in a 16-oz. flask and add to it 20 c.c. 
of absolute alcohol; dissolve the shellac in the alcohol by gentle 
heating. Now add slowly and with constant agitation 100 c.c. 
petrolic ether boiling below 8o° C. The first addition of petrolic 
ether to the alcoholic solution does not occasion the precipitation 
of any shellac, but as further quantities are added the mixed 
solvent of alcohol and petrolic ether becomes incapable of 
retaining the whole of the shellac in solution and it gradually 
precipitates out. It is necessary that the addition of the 
petrolic ether should therefore be made slowly and with stirring 
in order that the precipitating shellac may not carry out with it 
mechanically any of the rosin contained in the solution. When 
the whole of the 100 c.c. of petrolic ether has been added 100 c.c. 
of water is added also with agitation. The first additions of 
water cause the separation of the liquid into two layers one of 
which is rather strong alcohol, which may dissolve some part of 
the rosin which is afterward precipitated by the rest of the 
water. The necessity for agitation during this stage is to insure 
the collection into the petrolic ether of all the rosin. When 
all the water has been added the liquid is poured into a tapped 
separator and the flask rinsed out with a little more petrolic 
ether. The two liquids in the separator readily separate and 
the watery layer is drawn off. The petrolic ether is then washed 
with a little water which is also drawn off. The petrolic ether 
is then filtered into a clean separator and to it is added 25 c.c. 
of a solution of N/5 caustic soda in 50 per cent, alcohol. This 
caustic soda solution is measured into the separator accurately 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 75 

with a pipette and a similar pipette full of the same solution is 
titrated with standard hydrochloric acid, using methyl orange 
as an indicator. The separator containing the alcoholic soda 
solution and the petrolic ether is then thoroughly agitated, 
allowed to settle, and the watery layer drawn off into a tared flat, 
bottomed dish. The petrolic ether is then washed by agitating 
with a little 50 per cent, alcohol and the washings are added 
to the tared dish. There is further added to the contents of the 
tared dish the same volume of the same standard hydrochloric 
acid as were required by the check portion of 25 c.c. of the N/5 
soda. % In this way the entire quantity of soda is neutralized 
with hydrochloric acid and the resinous matters contained in the 
solution are left uncombined. The contents of- the dish are then 
allowed to evaporate at a low temperature until the residue is 
dry, when the dish with its contents is weighed. The check 
portion of 25 c.c. of N/5 soda is, after being neutralized with 
standard acid as described, evaporated in a similar dish and in 
this way the amount of sodium chloride produced from the 
25 c.c. portion is ascertained. By deducting the weight of 
sodium chloride so found from the combined weight of the 
resinous matter and sodium chloride the weight of the former is 
ascertained. The dried contents of the dish may now be further 
examined. The odor of the resin and its consistency may be 
observed, its acidity may be determined by solution in neutral 
alcohol and titration with N/10 alkali or if it is desired the 
resinous matter may be separated from the sodium chloride by 
dissolving it in ether or some other solvent. 

By this process it is practicable to actually separate, examine, 
and exhibit the rosin which had been added to the shellac as an 
adulterant. It is also practicable to determine the amount of 
wax present providing, however, that a much larger amount 
of petrolic ether had been used than is necessary for the complete 
extraction of rosin alone. It has been found necessary to use 
at least 200 c.c. of petrolic ether per gram of shellac in order to 
insure the complete extraction of the wax, while 50 c.c. of petrolic 
ether per gram of shellac appears quite sufficient to extract any 
reasonable amount of rosin. 

As previously stated the petrolic ether dissolves traces of 
pure shellac. It becomes important, therefore, to know how 
much will be dissolved from pure shellac when examined by the 



7 6 



ANALYSIS OF PAINTS AND PAINTING MATERIALS. 



process above described. A great many pure shellacs have 
therefore been examined by this process and at the same time 
their iodine figures have been ascertained by the Wijs-Langmuir 
process. The following figures are representative of the results 
obtained : 



Grade 



Iodine 
figure 



Angelo-B-Pure Button . 14.7 

Pure T-N 18.0 

Pure T-N 17.7 

Pure T-N 16.0 

Pure T-N 15.9 

Pure T-N 17.6 

Pure orange 17.4 

Sticklac 14 . 7 



% Extract- 
ed matter 



2 

1 
1 
2 

2 
1 
1 

3 



12 

79 

05 

19 

03 
82 

38 
07 



Acidity of extracted 
matter per 2 grams 
1 in c.c. N/10 KOH. 



1.6 

i-5 
0.8 

1.6 

15 

1-5 
1.2 

2.3 



It will be noted that there seems to be a tendency for the 
higher grades to give a larger amount of rosin soluble in petrolic 
ether than the lower grades. The amount given by such grades 
of shellac as are likely to be found adulterated may safely be 
assumed to be less than 2 per cent. If the shellac is of the highest 
grades, those which seldom contain rosin and which consequently 
seldom need to be examined by the analyst, the amount of soluble 
matter may with safety be assumed to be less than 3 per cent. 

The rosin which is to be determined consists principally of 
acid bodies which readily unite with caustic soda, but it also con- 
tains a certain amount of unsaponifiable matter which is not 
extracted from the petrolic ether by the soda solution. The 
amount of rosin which is finally weighed cannot, therefore, be 
greater than the amount of free acids originally contained in it. 
The amount of unsaponifiable matter contained in the rosin used 
is, therefore a matter of interest, but unfortunately it is impossi- 
ble to ascertain the exact amount. It is reasonable to assume, 
however, that not more than 85 per cent, of the rosin will be 
recovered and weighed in the process above described. This 
assumption agrees perfectly with the experience in this labora- 
tory in working upon a considerable variety of rosins. 



THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 77 

In calculating the amount of rosin content from the weight 
of extracted resinous matter in this process, allowance must be 
made for the small amount of pure shellac extracted and also for 
the shortage in the weight of rosin as finally weighed on account 
of the unsaponifiable matters contained in it. 

In making this calculation the following formula is used : 

If Y=per cent, rosin, 

M =per cent, of extract of pure shellac, 
N =per cent, of extract of pure rosin. 
A=per cent, of extract of mixture, 

-n^ v IO ° ( A ~ M ) 

Here M=2.o or in the case of high grade shellac, 3.0, and 

N=85.o. 

100 (A — 2). 



Then Y = 



83 



Shellac varnishes may contain beside true shellac not only 
rosin, but other gums and resins soluble in alcohol. It becomes, 
therefore, a matter of interest to ascertain how some of these 
other resins behave when treated by this process. Two samples 
of manilla, when treated, using absolute alcohol as the first 
solvent, gave, respectively, 41.2 and 43.3 per cent, of matter 
soluble in petroleum ether. The acidity of these two lots of 
matter soluble in petroleum ether was in the case of the first 
sample such that 1 c.c. of normal alkali neutralized 411. 7 mg. 
and in the case of the second 470.7 mg. Two samples of 
Kauri gave, respectively, 37.9 and 27.0 per cent. Upon 
titrating with standard alkali these portions soluble in petro- 
leum ether, it appeared that 1 c.c. of normal alkali was 
capable of neutralizing 903.6 mg. and 742.5 mg., respectively. 
Of Sandarac, two samples, when similarly. analyzed, gave 34.96 
and 36.19 per cent., having such an acidity that of the first 541.2 
mg. would neutralize 1 c.c. normal alkali, and of the second 
552.5 mg. would neutralize 1 c.c. Of Dammar, 89.9 per cent, 
proved to be soluble, while the resin of Shorea roburta, a sample 
of which was kindly sent by Mr. W. Risdon Criper, of Calcutta, 
gave 69 . 5 per cent, of soluble matter. 



APPENDIX A. 
THE ANALYSIS OF BITUMINOUS PAINTS. 

At the present time many bitumens and artificial bitumens 
are frequently used, either alone or in combination, in the 
manufacture of paints, black varnishes, and japans. The as- 
phaltic compounds are naturally occurring products in many 
cases containing comparatively large percentages of sulphur. 
Mineral matter, which is present in widely varying roportions, 
consists usually of limestone, clay, or sandstone, containing the 
usual impurities found in these materials. 

Petroleum residuum and coal-tar pitch are sometimes used 
alone as paints, but more frequently petroleum residuum is 
added to asphaltic compounds as a flux. Free carbon also finds 
application as a color agent for deepening such mixtures, but 
experience has shown that the percentage of free carbon should 
not exceed 20 per cent. 

While a chemical analysis of such mixtures will disclose little 
concerning their true value as paints, nevertheless it is in many 
cases advisable and necessary that an examination be made so 
as to determine their general composition. The following 
methods will be found to give good approximate results in the 
examination of paints made from asphaltic and bituminous 
compounds. 

Separation and Determination of Volatile Constituents. — 
100 grams of the paint, after being thoroughly mixed, are placed 
in a distilling flask and the volatile constituents separated in 
the usual way, as described on page 66, all the volatile con- 
stituents distilling over up to 180 C. being carefully collected. 
The amount of distillate thus found will give the percentage of 
volatile constituents present. The distillate is then fractionated 
so as to determine the percentage of benzol, benzene, turpentine, 
and volatile oils. This operation is carried out by the usual 
fractionation methods, fractions being weighed and the percent- 
age of each constituent determined. Separation and estimation 

78 



ANALYSIS OF BITUMINOUS PAINTS. 79 

of the turpentine in the distillate is best done by the polymer- 
ization method described on page 62. 

Any water present in the vehicle or in the asphalt itself, 
as so frequently occurs in asphaltic mixtures, will distil over 
at the above temperature and will be found in the distillate. 

It must also be understood that some low-boiling oils which 
are so often present in bituminous mixtures may distil over 
at or below 180 C. When such oils are present, it is impossible 
to differentiate between them and the oils present in the vehicle. 
In such cases, however, they may be assumed to act in the 
r61e of vehicle and may be reported as such. 

Nonvolatile Residue. — The residue left in the flask after 
distillation is then examined for bituminous matter (petrolene 
and asphaltene), nonbituminous matter, carbon, sulphur, and* 
the constituents entering into the ash. 

Petrolene and asphaltene are the names applied to the sub- 
stances obtained by the use of certain solvents on the natural 
and artificial bitumens. The portion soluble in petroleum spirit, 
ether, or acetone is known as petrolene, while the portion in- 
soluble in petroleum spirit but dissolved by boiling turpentine 
and cold chloroform is known as asphaltene. 

The total bituminous matter is considered to be that portion 
of the asphaltic mixture which is soluble in the above solvents 
or in carbon bisulphide, the portion insoluble being considered 
. as nonbituminous matter. Pure asphalt, as used in the manu- 
facture of painting materials, should be completely soluble 
(with the exception of 4 or 5 per cent, which may be mineral 
matter) in carbon disulphide, oil of turpentine, or chloroform. 

Nonbituminous Matter, Carbon, and Ash. — The residue remain- 
ing after the extraction by the carbon bisulphide method is dried 
and weighed. The loss between the original weight of the non- 
volatile residue and the weight of the unextracted matter^ gives 
the percentage of bituminous matter (asphaltene and petrolene) 
present. The insoluble residue after weighing is ignited until 
all the carbon has been burned off. The weight is again taken 
and the loss reported as nonbituminous matter and carbon. It 
is advisable before weighing to treat the ash with a little am- 
monium carbonate to reconvert any carbonates which may have 
been decomposed by the heating to their original form. 

Ash. — The constituents of the ash are determined in the 



80 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

manner outlined under the analysis of mixed pigments, or by 
any of the methods used in the analysis of limestones, clays, 
or sandstones. 

The mineral matter present quite frequently exists in com- 
bination with the bituminous matter forming resinous-like 
compounds which partially dissolve in the solvents used for 
fractionation of the nonvolatile residue, thus giving high results 
for the bituminous matter and low results for ash. These 
errors, however, serve to counterbalance each other and are 
frequently so inappreciable that they may be neglected. 

The correct percentage of ash should be determined by ignit- 
ing a new sample of the nonvolatile residue until all the carbon 
has been destroyed. 

Sulphur. — It is often necessary that the sulphur content of 
asphaltic mixtures be determined. This may be approximately 
determined by following Eschka's method : 

Mix intimately i gram of the finely ground, nonvolatile 
residue with i gram of calcined magnesium oxide and . 5 gram 
of mixed sodium-potassium carbonates, in a platinum or porce- 
lain crucible. After thorough mixing, the crucible (uncovered) 
is heated to a dull red heat with an alcohol or Bunsen flame, 
in the latter case the crucible being placed in a hole cut into an 
asbestos board, thus preventing any sulphur from the flame 
from contaminating the mixture. The action is hastened by 
frequent stirring of the mixture. The heating is continued 
until the contents of the crucible become a dull yellow. Cool 
the crucible and mix the contents intimately with about 1 gram 
finely powdered ammonium nitrate. Heat until the ammonium 
nitrate is completely decomposed. Any sulphites formed by the 
first treatment are thus completely converted into sulphates. 

The contents of the crucible, after cooling, are carefully 
transferred to a beaker and extracted with hot water. Evapo- 
rate, wash, acidify with hydrochloric acid and precipitate the 
sulphate present in the usual way with barium chloride. Weigh 
as barium sulphate and calculate to free sulphur. It has been 
found that the sodium peroxide method is apt to give results 
wnich are low. 

The Hempel- Graefe * method for determining the percent- 

* J. of Ind. and Eng. Chem., May, 1910, p. 187. 



ANALYSIS OF BITUMINOUS PAINTS. 8l 

age of sulphur in bitumens or pyro-bitumens, consists in burn- 
ing a small quantity of the material under examination, in an 
atmosphere of oxygen, with absorption of the gas in sodium 
peroxide. Subsequent neutralization and precipitation is made. 
In determining the presence and identification of vegetable 
or fossil gums, such as rosin or kauri gums, the methods of Mc- 
Ilhiney for the analysis of shellac together with the methods 
given for the analysis of varnish will prove useful. 

Examination of the Nonvolatile Residue. 

A portion of about 50 grams of the nonvolatile residue is 
placed in an Erlenmeyer flask and shaken with a considerable 
quantity of carbon bisulphide. After sufficient time has elapsed 
for the carbon bisulphide to exert its solvent power on the petro- 
lene and asphaltene, the contents of the flask are poured upon a 
suitable filter. If pigments are present, they will be found upon 
the filter and may be examined by the methods outlined for the 
analysis of pigments in mixed paints. 

If drying oils, such as linseed oil, are present in the non- 
volatile residue, they may be removed by treating another por- 
tion of the residue with 88° gasolene for eight or ten hours. 
Evaporation of the filtrate from this product will leave the oils 
which may be present in a condition suitable for analysis. 
Rosin and resinates are also extracted by this treatment and 
should be looked for. Fossil gums, however, are apt to be pre- 
cipitated by the gasolene. 

FORREST METHODS. 

The Examination of Black Varnishes and Enamels. 

The following method for the examination of paints contain- 
ing bitumens or pyro bitumens has been prepared for this book 
by Mr. C. N. Forrest, Chief Chemist of the New York Testing 
Laboratory, where extensive tests on the nature of bituminous 
materials have been conducted. These methods are of great im- 
portance and serve to give much new information regarding 
Bituminous Paints. 
6 



82 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

For the purpose of an analysis, bituminous paints should be 
divided into three classes, as follows: 

Asphaltum varnish. 
Asphaltum enamel. 
Coal-tar enamel. 

Asphaltum varnish, as its name implies, does not contain a 
pigment but consists of a base of asphatum and other substances, 
reduced, to a fluid consistency with a suitable volatile solvent. 

Asphaltum enamel consists of an asphaltum varnish in com- 
bination with a pigment, and may be either black or colored. 

Coal-tar enamel, although generally considered as a varnish 
or paint, always contains carbon in suspension and therefore 
should be classified as an enamel. 

A distinctive feature of bituminous varnishes and enamels 
is that they dry by evaporation rather than by oxidation. If a 
drying oil is present a certain degree of hardening of the film 
subsequently occurs, but the intinal drying of such varnishes 
and enamels depends upon the spontaneous evaparation of the 
volatile thinners present, and the rapidity of drying upon the 
degree of volatility of the volatile solvent. Any linseed or other 
oil present should be considered as a constituent of the base. 

An asphaltum varnish will therefore consist of a basic ma- 
terial dissolved in from 25 to 60 per cent, of some volatile solvent, 
such as turpentine, benzine, heavy petroleum spirit, or coal-tar 
spirit. Occasionally carbon disulphide or some special solvent 
may be employed, but that would be unusual. 

An asphaltum enamel will contain black or colored pigments 
combined with a varnish of essentially the same nature as has 
just been described. 

A coal-tar enamel will consist essentially of a base of coal- 
tar pitch dissolved in benzole or other coal-tar spirit. The free 
carbon present is very finely divided and will remain suspended 
for an indefinite period. 

There are several kinds of hard asphaltum available for var- 
nish-making, but fhe principal and most generally used types 
are mentioned in the following table, which also gives the im- 
portant characteristics of the same. 



ANALYSIS OF BITUMINOUS PAINTS. 



83 



Gilsonite. 



Nanjak. 



Grahamite. 



Refined 

Bermudez 

asphalt. 



Gil 
pitch. 



-> — 



Specific gravity at 

77° F 

Color of powder 

Melting-point 

Bitumen soluble in 

CS 2 

Mineral matter 
Difference 



1 .049 
Brown. 

325°F- 

99-9% 
. 1 

.0 



15 -9 
13-4 
None. 



100. o 
Bitumen soluble in 

88° naphtha ! 15.9 

This is per cent, of ' 

total bitumen. . . 

Residual coke . 

Paraffine 

Characteristics o f 

asphaltenes i n - 

soluble in 88° 

naphtha. 

Color 

Condition 

Residual coke . 



Black. 
Hard. 



1 .0844 

Dark 

brown. 

35o°F. 

99.2% 

•3 
•5 



i . 171 
Black. 

Intumesces. 

94-i% 

5-7 
.2 



1 00.0 

26.9 

27 .0 
25.0 
None. 



1 00.0 

• 4 

• 4 

53-3 
None. 



I-Q575 
Black. 

i7o°F. 

96.0% 
2 .0 
2 .0 

1 00.0 

69. 1 

71.9 
14.0 
None. 



Black. 
Hard. 



i5~ 20 % I 55-6o% 



Black. 
Hard. 

5o-55% 



Brown. 
Soft. 

30-35% 



1.0703 
Black. 

i64°F. 

98.2% 
Trace. 
1.8 

100. o 

69. 6 

709 

19-5 
.8 



Broisn. 

Soft. 

50-60% 



8 4 



ANALYSIS OF PAINTS AND PAINTING MATERIALS. 



The characteristics of the most select grades of coal-tar pitch 
suitable for the manufacture of enamel are as follows: 

Coal-tar Pitch. 



Hard. 



Specific gravity at 77°F 

Color of powder 

Melting-point 

Bitumen soluble in CS 2 

Mineral matter 

Free carbon, etc 

Bitumen soluble in 88° naphtha 

This is per cent, of total bitumen 

Residual coke 29.1 



Soft. 







1.24 


1.23 


Black. 


Black. 


i6i°F. 


i40°F. 


94- 1% 


92.2% 


. 1 


. 1 


S-8 


77 


I OO.O 


100. 


85.O 


87.0 


90-3 


94-4 



25-1 



The characteristics of the most select grade of stearine pitch, 
Calabrea pitch, and of the resins sometimes included in black 
varnishes are as follows: 



CALABRIA PITCH. 

Specific gravity at 7 7 F 1 . 030 

Color of powder Black. 

Melting-point 1 6i° F. 

Bitumen soluble in CS 2 99 . 5% 

Mineral matter .5 

100. o 

Bitumen soluble in 88° naphtha 41.3 

This is per cent, of total bitumen 41.5 

Residual coke n-5 

Characteristics of asphaltenes insoluble in 88° 
naphtha. 

Color Black. 

Condition Spongy — melts. 

Residual coke 21.8% 



ANALYSIS OF BITUMINOUS PAINTS. 



85 





Resins. 








Colophony. 


Kauri. 


Copal. 


Soluble in 88° naphtha 


100% 
Trace. 


4.0% 
Trace. 


25-0% 
Trace. 


Residual coke 







There is no established custom followed in the selection of 
the other materials which are combined witfi hard asphaltum 
in the preparation of the base of a varnish. 

Such materials include rosin, fossil gums, linseed oil, China 
wood-oil, mineral oil, driers, and other substances. The purpose 
of the use of such materials is to modify the degree of hardness 
and flexibility, facilitate the thinning operation and increase 
durability according to the service the finished varnish is to 
perform. 

A coal-tar enamel is usually nothing more than a coal-tar 
pitch dissolved in coal-tar spirit. It may sometimes contain 
rosin or a small amount of linseed oil, but that is unusual. It is 
not customary to mix coal-tar pitch and asphaltum for a varnish 
base as the two materials do not combine readily and, if com- 
bined, are furthermore generally but partially soluble in petro- 
leum spirit, the least costly solvent employed in this industry, 
x A practical test should always be made by applying a coat 
of the varnish or enamel on a surface similar to that upon which 
it is to be used and the covering or hiding capacity, spreading 
qualities, time of drying, etc., noted. An outdoor exposure test 
on a small steel plate of the materials intended for such use 
should also be made. 

The first step in the analysis of bituminous varnishes and 
enamels should be to separate the volatile thinners from the base, 
and this is most conveniently done by distilling about 50 grams 
in a flask by gentle heat. A nonoxidizing atmosphere should 
be maintained in the flask during the distillation by the intro- 
duction of CO, or other inert gas. The difference in the boiling- 
point of the solvent and the base is so great that a clean separa- 
tion may be readily made by this method. 

The temperature at which the volatile thinners pass over 
should be noted and a subsequent examination of the distillate 
for volume, specific gravity, flash-point, and indifference to strong 



86 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

sulphuric acid will give sufficient data for the identification of 
the same and the amount present. 

While the base in the distilling flask is still fluid it should 
be poured into a shallow tin box. The portion adhering to the 
flask may be removed with carbon disulphide, the solvent 
expelled, and the residue combined with the chief portion. This 
precaution, however, need not be observed unless a pigment is 
present. 

The amount of pigment may be determined by treating 10 to 
50 grams of the base with 100 c.c. carbon disulphide in a small 
Erlenmeyer flask and filtering through a Gooch crucible, washing 
with the same sovlent, or by extracting with carbon disulphide 
in a Soxhlet. 

Having separated the pigment as above and recovered the 
soluble portion by evaporating off the solvent, the analysis 
should proceed exactly as in the case of a clear asphaltum var- 
nish base. 

From 1 to 5 grams of the base, in a finely divided condition, 
should be treated in an Erlenmeyer flask with 100 to 200 c.c. 
88° naphtha and allowed to stand over night at laboratory 
temperature. The naphtha is then decanted through a Gooch 
or filter-paper, the residue transferred to the filter and washed 
with the solvent until the filtrate runs through clear. 

The filtrate will contain the rosin drying and petroleum oils 
and a portion of the asphaltum or pitch if any is present. 

The insoluble residue will consist essentially of the so-called 
asphaltenes of the asphaltum, and will generally represent from 
30 to 85 per cent, of the amount of asphaltum in the base, 
depending upon what variety of the same has been employed. 
In the case of Grahamite, it would represent practically all of the 
asphaltum present, but that material is not in general use in 
varnishes. 

The color and hardness of the insoluble residue should be 
noted and a determination of residual coke or fixed carbon 
made as follows: 

One gram of residue is ignited in a platinum crucible, as in 
the proximate analysis of coal, Jour. Amer. Chem. Soc., Vol. 21, 
p. 1 1 16, 1899. 

If the residue is dark brown and soft and has a fixed carbon 
of about 50 per cent, the asphaltum is probably an oil pitch. 



ANALYSIS OF BITUMINOUS PAINTS. 87 

If it is black and hard and has a fixed carbon of about 50 per 
cent, it is probably grahamite. If black and hard and about 
15 per cent, fixed carbon it is gilsonite. If dark brown and soft 
and about 30 per cent, fixed carbon it is probably Bermudez 
asphalt. 

The filtrate after expelling the solvent used in the extraction 
may be tested for saponification and iodine values and for rosin 
by the Lieberman or Storch test. If a quantitative separation 
of rosin is desired the laborious Twitchell method must be re- 
sorted to. 

The difference between the saponifiable and the total soluble 
in 88° naphtha will give the mineral oils and so-called petrolenes 
of the asphaltum. 

A positive test for and approximate determination of coal-tar 
may be made by distilling a small amount of the base in a glass 
retort to coke, and mixing 4 c.c. of the distillate thus obtained 
with 6 c.c. dimethyl sulphate in a graduated tube. Coal-tar 
distillates are entirely soluble in dimethyl sulphate, while those 
from asphaltum, petroleum, and vegetable paint oils and resins 
are insoluble. See Jour. Ind. and Eng. Chem., Vol. II, p. 186, 
May, 1910. 

The pigment separated from asphaltum enamels may be 
examined in detail if desired by the same methods employed in 
the analysis of linseed oil and house paint. 

The combinations in use by various manufacturers in the 
making of black varnishes are frequently very complicated. 

Baking enamels for certain specific uses require speicia 
formulae, but for the general line of black varnishes the princpall 
object is to produce a base of high gloss and deep color, having 
some flexibility, which will reduce with turpentine or benzine 
at a temperature sufficiently low to avoid excessive loss of 
solvent in the manufacturing process. 

To this end it is usually sufficient to fuse an asphaltum of 
the gilsonite type with rosin, linseed, or mineral oil in sufficient 
amount to reduce the melting-point of the asphaltum without 
rendering it unduly soft. 

The durability of the film of varnish is affected by the fluxing 
material used as well as its degree of hardness and flexibility, and 
the desire to produce a cheap varnish frequently overbalances 
the desire to produce a durable one. 



88 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

The base of a varnish for outdoor exposure to sunlight and 
atmospheric conditions should be of a different character both 
in degree of hardness and composition from varnishes intended 
for damp-proofing, insulating, and acid, and alkali resisting 
purposes. 

There is nothing to be gained by the use of turpentine and 
other expensive solvents instead of benzine or heavy petroleum 
spirit, provided the base is entirely soluble in the latter and a 
proper selection has been made to assure the drying properties 
desired. Varnish makers' benzine (62 °B.) evaporates too fast 
to be satisfactory as the thinning material of a heavy brush 
varnish. On the other hand, it is indispensable in thin quick : 
drying brush varnishes and dips. 

On account of the extremely complex nature of black varnish 
bases it is quite impossible to prescribe a general method which 
may be followed without modification and cover all features of 
this subject. 

The foregoing is, therefore, given more as an outline for the 
guidance of those analysts who are capable of adapting the 
general schemes of classification and separation to the particular 
purpose at hand, and supplementing the same with such further 
tests as will develop the special features of the material if the 
simple separations, etc., specifically mentioned are not sufficient. 



APPENDIX B. 

The following specifications of the Army and Navy Depart- 
ments are given so that the chemist engaged in the examination 
of such materials may become better acquainted with the 
requirements. These specifications, however, refer only to the 
chemical requirements, and for full specifications the reader is 
referred to the Bureau of Supplies and Accounts of the United 
States Navy, Washington, D. C. 

SPECIFICATIONS ISSUED BY THE ARMY DEPARTMENT. 

Pure White Lead. — White lead must be of the best quality, 
finely ground in pure well-settled raw linseed oil; must be of 
maximum whiteness; must work freely under the brush, and not 
be crystalline in structure nor deficient in density and opacity. 
Dry pigment must contain at least 98 per cent, of hydrate 
carbonate of lead. Its workings under the brush, maximum 
whiteness, body, and covering qualities to be determined by 
practical test. 

White Zinc. — American Process. — The dry pigment must 
contain at least 98 per cent, of oxide of zinc, not more than o . 5 
per cent, of sulphur in any form, and be of the quality known 
as "XX." 

French Process. — The dry pigment must contain at least 
99 per cent, of oxide of zinc and not more than 0.25 per cent, 
of sulphur in any form, and to be of maximum whiteness as 
compared with standard sample. 

Venetian Red. — The dry pigment must contain at least 40 
per cent, of sesquioxide of iron, not more than 15 per cent, of 
silica, the balance to consist of sulphate of lime that has been 
fully dehydrated by dead burning and rendered incapable of 
taking up water of crystallization. 

Indian Red. — Must be of good rich color. The dry pigment 
must contain at least 95 per cent, of oxide of iron (Fe 2 3 ), and 

89 



90 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

be free from sulphur and alkali. Pale shade is desired in the 
absence of other specifications. 

Vermilion. — American (dry). — Must be of good, bright color, 
and contain at least 98 per cent, of basic chromate of lead, and 
be free from any foreign coloring matters. 

English (dry). — Must contain at least 99 per cent, of red 
sulphide of mercury; must be free from any foreign coloring 
matters or alkali in any form. 

Artificial. — The dry pigment must be the lead-barium lake 
of the azo dye known commercially as " Lithol." 

Raw and Burnt Sienna. — The dry pigment must be equal 
in quality to the best selected Italian sienna, and must not 
contain more than 5 per cent, of lime in any form. 

Yellow Chromes. — Must be of good bright color and full 
strength. The dry pigment must contain at least 98 per cent, 
of normal chromate or basic chromate of lead. 

Yellow Ochre. — It must be equal in color and quality to the 
best French ochre and be free from any chromate of lead or 
foreign coloring matter. The dry pigment must contain at 
least 20 per cent, of oxide of iron and not more than 5 per cent, of 
lime in any form. 

Chrome Green. — Ghrome green must be of good bright color. 
The dry pigment must contain 25 per cent, chrome green made 
by mixture of pure chrome yellow and Russian blue and 75 per 
cent, barium sulphate. Medium shade is desired in absence of 
other specifications. 

Drop Black. — Drop black must be of good deep luster and 
consist of calcined bone-black only. The addition of blue or gas 
carbon-black will be ground for rejection. The paste must 
contain not less than 45 per cent, of pure pigment. 

Oil Lamp-black for Tinting Purposes. — The pigment must be 
the perfectly calcined product of oils only and show less than 
2 per cent, of ash. It must be absolutely neutral, ffee from oil 
or greasy matter, grit, and all impurities. The pigment reduced 
in white must give a clear blue-gray tone or tint. 

Japan Drier. — Japan drier must not flash below 103 F. 
(open tester) ; must be of the best quality and made from pure 
kauri gum, pure linseed oil, pure turpentine and the proper 
driers only; must set to touch in from one-fourth to one hour, 
dry elastic in from eighteen to twenty-four hours at a temperature 



PAINT SPECIFICATIONS. 9 1 

of 70 F., and must not rub up or powder under friction by the 
finger. When mixed with pure raw linseed oil in the proportion 
of eight parts of oil to one part of drier must remain clear for two 
hours and set to touch in from six to seven hours at a temperature 
of 70 F. 

Varnish. — All varnishes other than those which have definite 
specifications must be pure turpentine hard-gum varnishes and 
absolutely free from rosin or any turpentine substitutes. 

Damar Varnish. — It must be made from solution of the very 
best quality of damar gum; such solution to contain at least 50 
per cent, of gum with 45 per cent, turpentine. It must be digested 
cold and well settled. It must be as clear as and not darker 
than the standard sample. It must be free from benzine, rosin, 
and lime or other mineral matter. Its specific gravity at 6o° F. 
must be between . 935 and . 937 and its flash point between 105 
and 1 1 5 F. It must set to touch in not more than twenty 
minutes, and when mixed with pure zinc oxide must show a 
smooth glossy surface equal to that shown by the standard 
sample. 

Tests. — Besides chemical tests to determine the above quali- 
ties and practical tests to determine its qualities of finish, a 
board properly coated with a mixture of zinc and the liquid 
will be exposed to the weather for a period of one month, and at 
the end of this time must have stood such exposure equally as 
well as the standard sample. A similarly prepared sample will 
also be baked at 250 F., and must not at this temperature show 
any greater signs of cracking, blistering, or any other defects 
than standard samples under the same conditions. 

Asphaltum Varnish. — Asphaltum varnish must be made of 
pure high-grade asphaltum of the very best quality, of pure 
linseed oil and pure turpentine dryers only, and must not con- 
tain less than 20 gallons of prepared linseed oil tp 100 gallons 
of varnish. It must not flash below 103 F. (open tester). It 
must mix freely with raw linseed oil in all proportions; must 
be clear and free from sediment, resin, and naphtha. When 
flowed on glass and allowed to drain in a vertical position the 
film must be perfectly smooth and of full body, and must equal 
in this last respect the standard sample. It must set to touch 
in from one and one-half to two and one-half hours and must 
dry hard in less than twenty hours at 70 F. When dry and 



92 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

hard it must not rub up or powder under friction by the finger. 
The application of heat must quicken the time of drying and 
give a harder film. 

SPECIFICATIONS ISSUED BY THE NAVY DEPARTMENT. 

White Lead in Oil. — The dry pigment must be of the best 
quality, must not be crystalline in structure or deficient in 
density or opacity. Unless otherwise specified, white lead will 
be delivered in paste form, the pigment finely ground in pure 
raw linseed oil, and in paste form must not contain more than 
0.5 per cent, of moisture. The dry pigment must be a pure 
hydrated carbonate of lead, free from all adulterants, and equal 
in quality to the best commercial grades. The total acetate 
must not be in excess of the equivalent of 0.15 per cent, of 
absolute acetic acid. 

Specifications for Whiting. — The material must be free 
from grit; must contain not more than 1 .5 per cent, of matter 
insoluble in dilute hydrochloric acid, and not more than 4/10 
per cent, oxides of iron and aluminum (determined together). 

Specifications for Chrome Green. — The dry pigment must 
be of a good bright color and must contain at least 98 per cent, 
by weight of pure lemon chrome and Chinese blue, which mix- 
ture must not contain more than 10 per cent, by weight of 
lead sulphate and must be equal in all respects to the standard 
sample. A medium shade is desired in the absence of other 
specifications. 

Metallic Brown. — 1. The dry pigment must contain not 
less than 45 per cent., by weight, of oxide of iron and must not 
contain more sulphur in combination than the equivalent of 
2 per cent., by weight, of sulphur trioxide (S0 8 ). 

2. It must be ground perfectly pure, not made from or 
adulterated with the by-products of sulphuric acid works, and 
must be free from makeweights or adulterants. When in paste 
form, it must contain at least 20 per cent., by weight, of pure 
raw linseed oil. 

Chinese Blue. — 1. The dry pigment must contain not less 
than 98 per cent., by weight, pure coloring matter of the best 
quality, free from adulterants, and equal in every respect to the 
standard sample. 



PAINT SPECIFICATIONS. 93 

2. When in paste form, the paste must contain not less than 
50 per cent, by weight of pure pigment ground in absolutely 
pure, well-settled, and perfectly clear raw linseed oil of the best 
quality only to a medium stiff consistency, which will break up 
readily in thinning, and must be free from grit, adulterants, and 
all impurities. 

Red Lead, Dry. — The dry pigment must be of the best 
quality, free from all adulterants, and contain at least 94 per 
cent, of true red lead( P 3°) — equivalent to 32.8 per cent, of 
lead peroxide ( Pb °) — , the balance to be practically pure lead 
monoxide (PbO). It must contain less than 0.1 per cent, of 
metallic lead, and to be of such fineness that not more than o . 5 
per cent, remains after washing with water through a No. 21 
silk bolting cloth sieve. It must be of good bright color and be 
equal to the standard sample in freedom from vitrified particles 
and in other respects. 

Chrome Yellow (Medium Orange). — i. The dry pigment must 
be of good bright color and full strength, and must contain at 
least 98 per cent, by weight of normal chromate or basic chro- 
ma te of lead. 

2. The pigment must be of the best quality, finely ground in 
absolutely pure, well-settled, and perfectly clear raw linseed oil of 
the best quality only to a medium stiff paste, which will break 
up readily in thinning, and must be free from grit, adulterants, 
and all impurities. 

Specifications for Spar Varnish. — i. To be of the best quality 
and manufacture and equal in all respects, including body, 
covering properties, gloss, finish, and durability, to the standard 
sample in the general storekeepers' offices at the various navy 
yards. To be made exclusively from the best grade of hard- 
varnish resins, pure linseed oil, pure turpentine, and lead- 
manganese driers, and to be free from all adulterants or other 
foreign materials. 

2. The varnish must not flash below 105 F. (open tester), and 
when flowed on glass must set to touch in from six to twelve 
hours and dry hard in from thirty to forty-eight hours at a 
temperature of 70 F. To be as clear as and not darker than the 
standard sample, and to be equal to it in all respects as above 
specified. 

Interior Varnish. — i. To be of the best quality and manu- 



94 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

facture and equal in all respects, including body, covering 
properties, gloss, finish, and durability, to the standard sample 
in the general storekeepers' offices at the various navy yards; 
to be made exclusively from the best grade of hard- varnish resins, 
pure linseed oil, pure spirits of turpentine, and lead-manganese 
driers, and to be free from all adulterants or other foreign 
materials. 

2. The varnish must not flash below 105 F. (open tester), 
set to touch in from six to eight hours and dry hard within 
twenty-four hours in a temperature of 70 F. It must stand 
rubbing with pumice-stone and water in thirty-six hours without 
sweating, and must polish in seventy-two hours with rottenstone 
and water; to be as clear as and not darker than the standard 
sample and to be equal to it in all respects, as above specified. 

Japan Drier. — 1. Japan drier must not flash below 105 F. 
(open tester); must be of the best quality, light in color, and 
be made from pure kauri resin, pure linseed oil, pure spirits of 
turpentine, and lead-manganese driers, and be free from adulter- 
ants, foreign material, sediment, and suspended matter. When 
flowed on a glass plate and allowed to drain in a vertical position 
the material must not come off when touched lightly with the 
finger after from fifteen to sixty minutes, and must dry elastic 
in not less than eight hours nor more than twenty-four hours 
at a temperature of 70 F., and must not rub up or powder under 
friction by the finger at the end of this time. When mixed with 
pure raw linseed oil (that will not break under 6oo° F.) in the 
proportion of eight parts of oil to one part of drier the mixture 
must remain clear for at least two hours, and when flowed on a 
glass plate must not come off when touched lightly with the 
finger at the end of eight hours at a temperature of about 70 F. 

Raw Linseed Oil. — Must be absolutely pure well-settled 
linseed oil of the best quality; must be perfectly clear and not 
show a loss of over 2 per cent, when heated to 212 F., or show 
any deposit of foots after being heated to that temperature. 
The specific gravity must be between 0.932 and 0.937 at 6o° F. 

To be purchased by the commercial gallon; to be inspected by 
weight, and the number of gallons to be determined at the rate 
of 7 1/2 pounds of oil to the gallon. 

Boiled Linseed Oil. — Must be absolutely pure kettle-boiled oil 
of the best quality, and the film left after flowing the oil over 



PAINT SPECIFICATIONS. 95 

glass and allowing it to drain in a vertical position must dry free 
from tackiness in twelve hours at a temperature of 70 F. 

It must contain no resin. The specific gravity must be 
between o . 934 and o . 940 at 6o° F. 

To be purchased by the commercial gallon; to be inspected by 
weight, and the number of gallons to be determined at the rate 
of 7 1/2 pounds of oil to the gallon. 

Spirits of Turpentine. — i. The turpentine must be the prop- 
erly prepared distillate of the resinous exudation of the proper 
kinds of live pine or live pitch pine, unmixed with any other 
substance; it must be pure, sweet, clear, and white, and must 
have characteristic odor. 

2. A single drop allowed to fall on white paper must com- 
pletely evaporate at a temperature of 70 F. without leaving a 
stain. 

3. The specific gravity must not be less than 0.862 or greater 
than 0.872 at a temperature of 6o° F. 

4. When subjected to distillation, not less than 95 per cent, 
of the liquid should pass over between the temperature of 308 
F. and 330 F., and the residue should show nothing but the 
heavier ingredients of pure spirits of turpentine. If at the begin- 
ning of the operation it shows a distillation point lower than 305 
F., this will constitute a cause for rejection. 

5. A definite quantity of the turpentine is to be put in an 
open dish to evaporate, and the temperature of the dish will be 
maintained at 21 2 F.; if a residue greater than 2 per cent, of the 
quantity remains on the dish it will constitute a cause for 
rejection. 

6. Flash Tests. — An open tester is to be filled within 1/4 inch 
of its rim with the turpentine, which may be drawn at will 
from any one can of the lot offered under the proposal. The 
tester thus filled will be floated on water contained in a metal 
receptacle. The temperature of the water will be gradually and 
steadily raised from its normal temperature of about 6o° F. by 
applying a gas or spirit flame under the receptacle. The tem- 
perature of the water is to be increased at the uniform rate of 2 F. 
per minute. The taper should consist of a fine linen or cotton 
twine (which burns with a steady flame), unsaturated with any 
substance. When lighted it is to be used at every increase of 
i° temperature, beginning at ioo° F. It is to be drawn horizon- 



96 ANALYSIS OF PAINTS AND PAINTING MATERIALS. 

tally over the surface of the turpentine and on a level with the 
rim of the tester. The temperature will be determined by plac- 
ing a thermometer in the turpentine contained in the tester so 
that the bulb will be wholly immersed in the liquid. The 
turpentine must not flash below 105 F. 

7. Sulphuric Acid Test. — Into a 30 cubic centimeter tube, 
graduated to tenths, put 6 cubic centimeters of the spirits of 
turpentine to be examined. Hold the tube under the spigot and 
then slowly fill it nearly to the top of the graduation with con- 
centrated oil of vitriol. Allow the whole mass to become cool 
and then cork the tube and mix by shaking the tube well, cooling 
with water during the operation if necessary. Set the tube ver- 
tical and allow it to stand at the ordinary temperature of the 
room and not less than half an hour. The amount of clear layer 
above the mass shows whether the material passes test or not. 
If more than 6 per cent, of the material remains undissolved 
in the acid this will constitute a cause for rejection. 



INDEX. 



Acetic acid, in white lead, 4 
Thompson's method, 4 
navy method, 5 

Acid number, linseed oil, 52 

Aluminium, determination in 
mixed pigments, 4 1 
separation from iron, 41-34 
separation from chromium, 3 7 

American vermilion, analysis of, 

35 
Antwerp blue, analysis of, 33 

commercial method, 34 

Asbestine, analysis of, 23 

Asphaltene, determination of, 79-86 

Asphaltic compounds, distinction 

from coal-tar compounds, 

87 
paints, analysis of, 78 

Asphaltum varnish, specincations, 

army, 91 

B 

Barium sulphate, determination of, 
21 

in barytes, 2 1 

in blanc fixe, 2 1 

in lithopone, 20 

in mixed paints, 41, 44, 46 
Barytes, analysis of, 2 1 
Basic carbonate white lead, anal- 
ysis of, 3 

sulphate white lead, analysis 
of, 17 
Benzine, analysis of, 64 
Bituminous paints, analysis of, 78 
Black pigments, analysis of, 38 
Blanc fixe, analysis of, 2 1 
Blue pigments, analysis of, 3 2 



Calcium, determination of, 22 
as oxalate, 22 
volumetric method, 23 
carbonate, analysis of, 2 2 
sulphate, analysis of, 22 
Thompson's method, 45 

Carbon dioxide, determination of, 

4 
De Horvath method, 1 5 

Scheibler's method, '6 

China clay, analysis of, 23 

Chinese blue, analysis of, 33 

commercial method, 34 

specifications, navy, 92 

wood oil, examination of, 61 

Chromium, determination of, 3 5, 3 7 

as oxide, 35 

separation from aluminum, 3 7 

separation from iron, 3 7 

Chromes, specifications, army, 90 

Chrome green, analysis of, 36 

specifications, army, 36 

yellow, analysis of, 3 5 

specifications, navy, 92, 93 

Coal-tar compounds, distinction 

from asphaltic compounds, 

87 



Damar varnish, specifications, 

army, 91 
Dietrich Tables, 9 
Driers, japan, analysis of, 65 
Drop black, analysis of, 3 8 
specifications, army, 90 

£ 

Eschka's method, sulphur, 80 



97 



9« 



IDNEX. 



Ferrocyanide solution, standard for 

volumetric zinc, 2 
Flash-point, linseed oil, 50 
Foots, linseed oil, 50 

G 

Graphite, analysis of, 38 
Green pigments, analysis of, 36 
Gypsum, analysis of, 22 

H 

Hexabromide test, linseed oil, 53 
Hughes' method, sublimed white 
lead, 17 



Indian red, analysis of, 26 

specifications, army, 89 
Interior varnish, specifications, 

navy, 93 
Iodine values, linseed oil, 52 

mixed oils, 60 
Iron, determination of, 27, 41 

as oxide, 4 1 

in mixed paints, 41 

in oxides, 27 

separation from aluminum, 

4i,34 
from chromium, 37 
volumetric, bichromate 

method, 25 
permanganate method, 27 

j 

Japan, analysis of, 65 

Mcllhiney's method, 67 
driers, analysis of, 65 
specifications, army, 90 

L 

Lamp-black, analysis of, 38 
specifications, army, 90 

Lead, as chromate, 4 
as sulphate, 3 
volumetric method, 6 
in mixed paints, 41, 43, 44, 47 
impurities in metallic lead, 1 6 



Lead chromate, analysis of, 35 
dioxide, determination, volu- 
metric method, 28 
sulphite, determination, 
Thompson's method, 47 
Leaded zinc, analysis of, 18 
Lemon chrome, analysis of, 3 5 
Light petroleum oils, analysis of, 

64 
Linseed oil, analysis of, 49 

boiled, specifications, navy, 

94 
flash-point, 50 
foots, 50 
iodine values, 52 
raw, specifications, navy, 94 

M 

Magnesium, determination as pyro- 
phosphate, 24 
Mannhardt's method, o c h e r s , 

siennas, umbers, 25 
Maumene test, 55 
Mcllhiney's method, for Japan, 67 
for shellac, 7 1 
for varnish, 67 
Mercury, gravimetric methods, 30 
Metallic brown, analysis of, 26 

specifications, navy, 92 
Mineral black, analysis of, 3 8 
Mixed paints and pigments, analy- 
sis of, 40 
Thompson's methods, 43 
Mixed colored paints and pig- 
ments, analysis of, 47 

N 

Navy specifications, 92 



Ocher, analysis of, 2 5 

specifications, army, 90 

Oil lamp-black, specifications, 
army, 90 

Orange chrome, analysis of, 3 5 
mineral, analysis of, 28 
pigments, analysis of, 35 



• •• • 






•.. ..•••.:..:: ••••••• •••• • 



INDEX. 



99 



Organic colors in pigments, exam- 
ination of , 3 1 



Paint vehicle, analysis of, 48 

separation from pigment, 40, 48 
Paris white, analysis of, 22 
Petrolene, determination of, 78 
Petroleum oils, analysis of, 64 
Prussian blue, analysis of, 33 
commercial method, 33 

R 

Red lead, analysis of, 28 
specifications, navy, 93 
pigments, analysis of, 28 
Rosin, 53 

in linseed oil, 53, 58 
oil, determination of, 53 
Lewkowitsch's method, 58 
gravimetric method, 59 
volumetric method, 58 
as an adulterant, 7 1 



Saponification number, linseed oil, 

Separation vehicle from pigment, 

40, 48 
Shellac, analysis of, 7 1 

Mcllhiney's method, 7 1 
Sienna, analysis of, 2 5 

specifications, army, 90 
Silex, analysis of, 23 
Silica, analysis of, 23 

in mixed paints, 46 
Sodium, determination of, 24 

as chloride, 25 

as sulphate, 2 5 

separation from potassium, 2 5 
Soluble sulphates, in barytes and 

blanc fixe, 22 
Solvent, for extraction of vehicle 

from pigment, 40 
Soya bean oil, examination of, 59 
Spar varnish, specifications, navy, 
93 



Specifications, army, 89 

navy, 92 
Spirits of turpentine, analysis of, 
62 
specifications, navy, 95 
Sublimed white lead, complete 

analysis, 17 
Sulphates, in barytes and blanc 
fixe, 22 
in sublimed white lead, 1 7 
Sulphur, Eschka's method, in as- 
phaltic and bituminous 
compounds, 80 
in ultramarine blue, 33 
Sulphur dioxide, in sublimed white 
lead, 18 



Turpentine, spirits of, analysis of, 
61 
specifications, navy, 95 



U 



Ultramarine blue, average com- 
position, 33 



Varnish, analysis of, 65 

damar, specifications, army, 

9i 
interior, specifications, navy, 

93 
Mcllhiney's method, 67 

spar, specifications, navy, 93 

specifications, army, 91 
Vehicle, analysis of, 48 

separation from pigment, 40, 4 8 
Venetian red, analysis of, 26 

specifications, army, 89 
Vermilion, analysis of, 29 

specifications, army, 90 
Viscosity, linseed oil, 49 

W 

Water, in vehicle, Nemzek method, 
48 



• r • 



:- . 



• •• 



v : •-• • • • 



•*• • : •: ••: ••• ••• 

•••••«•••••• •••• • •• • 



ioo 



INDEX. 



White lead, analysis of, 3 
specifications, army, 8y 
navy, 92 
White pigments, analysis of, 1 
Whiting, analysis of, 22 
specifications, navy, 92 



Zinc, determination of, 1 



Zinc, as oxide, 1 

volumetric method, 1 
in mixed paints, 42 

Zinc chromate, analysis of, 35 
lead, analysis of, 18 
oxide, analysis of, 1 

specifications, army, 89 
sulphide, in lithopone, 20